/*------------------------------------------------------------------------- * * nbtutils.c * Utility code for Postgres btree implementation. * * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/access/nbtree/nbtutils.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include "access/nbtree.h" #include "access/reloptions.h" #include "commands/progress.h" #include "miscadmin.h" #include "utils/datum.h" #include "utils/lsyscache.h" #define LOOK_AHEAD_REQUIRED_RECHECKS 3 #define LOOK_AHEAD_DEFAULT_DISTANCE 5 #define NSKIPADVANCES_THRESHOLD 3 static inline int32 _bt_compare_array_skey(FmgrInfo *orderproc, Datum tupdatum, bool tupnull, Datum arrdatum, ScanKey cur); static void _bt_binsrch_skiparray_skey(bool cur_elem_trig, ScanDirection dir, Datum tupdatum, bool tupnull, BTArrayKeyInfo *array, ScanKey cur, int32 *set_elem_result); static void _bt_skiparray_set_element(Relation rel, ScanKey skey, BTArrayKeyInfo *array, int32 set_elem_result, Datum tupdatum, bool tupnull); static void _bt_skiparray_set_isnull(Relation rel, ScanKey skey, BTArrayKeyInfo *array); static void _bt_array_set_low_or_high(Relation rel, ScanKey skey, BTArrayKeyInfo *array, bool low_not_high); static bool _bt_array_decrement(Relation rel, ScanKey skey, BTArrayKeyInfo *array); static bool _bt_array_increment(Relation rel, ScanKey skey, BTArrayKeyInfo *array); static bool _bt_advance_array_keys_increment(IndexScanDesc scan, ScanDirection dir, bool *skip_array_set); static void _bt_rewind_nonrequired_arrays(IndexScanDesc scan, ScanDirection dir); static bool _bt_tuple_before_array_skeys(IndexScanDesc scan, ScanDirection dir, IndexTuple tuple, TupleDesc tupdesc, int tupnatts, bool readpagetup, int sktrig, bool *scanBehind); static bool _bt_advance_array_keys(IndexScanDesc scan, BTReadPageState *pstate, IndexTuple tuple, int tupnatts, TupleDesc tupdesc, int sktrig, bool sktrig_required); #ifdef USE_ASSERT_CHECKING static bool _bt_verify_arrays_bt_first(IndexScanDesc scan, ScanDirection dir); static bool _bt_verify_keys_with_arraykeys(IndexScanDesc scan); #endif static bool _bt_oppodir_checkkeys(IndexScanDesc scan, ScanDirection dir, IndexTuple finaltup); static bool _bt_check_compare(IndexScanDesc scan, ScanDirection dir, IndexTuple tuple, int tupnatts, TupleDesc tupdesc, bool advancenonrequired, bool forcenonrequired, bool *continuescan, int *ikey); static bool _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, TupleDesc tupdesc, ScanDirection dir, bool forcenonrequired, bool *continuescan); static void _bt_checkkeys_look_ahead(IndexScanDesc scan, BTReadPageState *pstate, int tupnatts, TupleDesc tupdesc); static int _bt_keep_natts(Relation rel, IndexTuple lastleft, IndexTuple firstright, BTScanInsert itup_key); /* * _bt_mkscankey * Build an insertion scan key that contains comparison data from itup * as well as comparator routines appropriate to the key datatypes. * * The result is intended for use with _bt_compare() and _bt_truncate(). * Callers that don't need to fill out the insertion scankey arguments * (e.g. they use an ad-hoc comparison routine, or only need a scankey * for _bt_truncate()) can pass a NULL index tuple. The scankey will * be initialized as if an "all truncated" pivot tuple was passed * instead. * * Note that we may occasionally have to share lock the metapage to * determine whether or not the keys in the index are expected to be * unique (i.e. if this is a "heapkeyspace" index). We assume a * heapkeyspace index when caller passes a NULL tuple, allowing index * build callers to avoid accessing the non-existent metapage. We * also assume that the index is _not_ allequalimage when a NULL tuple * is passed; CREATE INDEX callers call _bt_allequalimage() to set the * field themselves. */ BTScanInsert _bt_mkscankey(Relation rel, IndexTuple itup) { BTScanInsert key; ScanKey skey; TupleDesc itupdesc; int indnkeyatts; int16 *indoption; int tupnatts; int i; itupdesc = RelationGetDescr(rel); indnkeyatts = IndexRelationGetNumberOfKeyAttributes(rel); indoption = rel->rd_indoption; tupnatts = itup ? BTreeTupleGetNAtts(itup, rel) : 0; Assert(tupnatts <= IndexRelationGetNumberOfAttributes(rel)); /* * We'll execute search using scan key constructed on key columns. * Truncated attributes and non-key attributes are omitted from the final * scan key. */ key = palloc(offsetof(BTScanInsertData, scankeys) + sizeof(ScanKeyData) * indnkeyatts); if (itup) _bt_metaversion(rel, &key->heapkeyspace, &key->allequalimage); else { /* Utility statement callers can set these fields themselves */ key->heapkeyspace = true; key->allequalimage = false; } key->anynullkeys = false; /* initial assumption */ key->nextkey = false; /* usual case, required by btinsert */ key->backward = false; /* usual case, required by btinsert */ key->keysz = Min(indnkeyatts, tupnatts); key->scantid = key->heapkeyspace && itup ? BTreeTupleGetHeapTID(itup) : NULL; skey = key->scankeys; for (i = 0; i < indnkeyatts; i++) { FmgrInfo *procinfo; Datum arg; bool null; int flags; /* * We can use the cached (default) support procs since no cross-type * comparison can be needed. */ procinfo = index_getprocinfo(rel, i + 1, BTORDER_PROC); /* * Key arguments built from truncated attributes (or when caller * provides no tuple) are defensively represented as NULL values. They * should never be used. */ if (i < tupnatts) arg = index_getattr(itup, i + 1, itupdesc, &null); else { arg = (Datum) 0; null = true; } flags = (null ? SK_ISNULL : 0) | (indoption[i] << SK_BT_INDOPTION_SHIFT); ScanKeyEntryInitializeWithInfo(&skey[i], flags, (AttrNumber) (i + 1), InvalidStrategy, InvalidOid, rel->rd_indcollation[i], procinfo, arg); /* Record if any key attribute is NULL (or truncated) */ if (null) key->anynullkeys = true; } /* * In NULLS NOT DISTINCT mode, we pretend that there are no null keys, so * that full uniqueness check is done. */ if (rel->rd_index->indnullsnotdistinct) key->anynullkeys = false; return key; } /* * free a retracement stack made by _bt_search. */ void _bt_freestack(BTStack stack) { BTStack ostack; while (stack != NULL) { ostack = stack; stack = stack->bts_parent; pfree(ostack); } } /* * _bt_compare_array_skey() -- apply array comparison function * * Compares caller's tuple attribute value to a scan key/array element. * Helper function used during binary searches of SK_SEARCHARRAY arrays. * * This routine returns: * <0 if tupdatum < arrdatum; * 0 if tupdatum == arrdatum; * >0 if tupdatum > arrdatum. * * This is essentially the same interface as _bt_compare: both functions * compare the value that they're searching for to a binary search pivot. * However, unlike _bt_compare, this function's "tuple argument" comes first, * while its "array/scankey argument" comes second. */ static inline int32 _bt_compare_array_skey(FmgrInfo *orderproc, Datum tupdatum, bool tupnull, Datum arrdatum, ScanKey cur) { int32 result = 0; Assert(cur->sk_strategy == BTEqualStrategyNumber); Assert(!(cur->sk_flags & (SK_BT_MINVAL | SK_BT_MAXVAL))); if (tupnull) /* NULL tupdatum */ { if (cur->sk_flags & SK_ISNULL) result = 0; /* NULL "=" NULL */ else if (cur->sk_flags & SK_BT_NULLS_FIRST) result = -1; /* NULL "<" NOT_NULL */ else result = 1; /* NULL ">" NOT_NULL */ } else if (cur->sk_flags & SK_ISNULL) /* NOT_NULL tupdatum, NULL arrdatum */ { if (cur->sk_flags & SK_BT_NULLS_FIRST) result = 1; /* NOT_NULL ">" NULL */ else result = -1; /* NOT_NULL "<" NULL */ } else { /* * Like _bt_compare, we need to be careful of cross-type comparisons, * so the left value has to be the value that came from an index tuple */ result = DatumGetInt32(FunctionCall2Coll(orderproc, cur->sk_collation, tupdatum, arrdatum)); /* * We flip the sign by following the obvious rule: flip whenever the * column is a DESC column. * * _bt_compare does it the wrong way around (flip when *ASC*) in order * to compensate for passing its orderproc arguments backwards. We * don't need to play these games because we find it natural to pass * tupdatum as the left value (and arrdatum as the right value). */ if (cur->sk_flags & SK_BT_DESC) INVERT_COMPARE_RESULT(result); } return result; } /* * _bt_binsrch_array_skey() -- Binary search for next matching array key * * Returns an index to the first array element >= caller's tupdatum argument. * This convention is more natural for forwards scan callers, but that can't * really matter to backwards scan callers. Both callers require handling for * the case where the match we return is < tupdatum, and symmetric handling * for the case where our best match is > tupdatum. * * Also sets *set_elem_result to the result _bt_compare_array_skey returned * when we used it to compare the matching array element to tupdatum/tupnull. * * cur_elem_trig indicates if array advancement was triggered by this array's * scan key, and that the array is for a required scan key. We can apply this * information to find the next matching array element in the current scan * direction using far fewer comparisons (fewer on average, compared to naive * binary search). This scheme takes advantage of an important property of * required arrays: required arrays always advance in lockstep with the index * scan's progress through the index's key space. */ int _bt_binsrch_array_skey(FmgrInfo *orderproc, bool cur_elem_trig, ScanDirection dir, Datum tupdatum, bool tupnull, BTArrayKeyInfo *array, ScanKey cur, int32 *set_elem_result) { int low_elem = 0, mid_elem = -1, high_elem = array->num_elems - 1, result = 0; Datum arrdatum; Assert(cur->sk_flags & SK_SEARCHARRAY); Assert(!(cur->sk_flags & SK_BT_SKIP)); Assert(!(cur->sk_flags & SK_ISNULL)); /* SAOP arrays never have NULLs */ Assert(cur->sk_strategy == BTEqualStrategyNumber); if (cur_elem_trig) { Assert(!ScanDirectionIsNoMovement(dir)); Assert(cur->sk_flags & SK_BT_REQFWD); /* * When the scan key that triggered array advancement is a required * array scan key, it is now certain that the current array element * (plus all prior elements relative to the current scan direction) * cannot possibly be at or ahead of the corresponding tuple value. * (_bt_checkkeys must have called _bt_tuple_before_array_skeys, which * makes sure this is true as a condition of advancing the arrays.) * * This makes it safe to exclude array elements up to and including * the former-current array element from our search. * * Separately, when array advancement was triggered by a required scan * key, the array element immediately after the former-current element * is often either an exact tupdatum match, or a "close by" near-match * (a near-match tupdatum is one whose key space falls _between_ the * former-current and new-current array elements). We'll detect both * cases via an optimistic comparison of the new search lower bound * (or new search upper bound in the case of backwards scans). */ if (ScanDirectionIsForward(dir)) { low_elem = array->cur_elem + 1; /* old cur_elem exhausted */ /* Compare prospective new cur_elem (also the new lower bound) */ if (high_elem >= low_elem) { arrdatum = array->elem_values[low_elem]; result = _bt_compare_array_skey(orderproc, tupdatum, tupnull, arrdatum, cur); if (result <= 0) { /* Optimistic comparison optimization worked out */ *set_elem_result = result; return low_elem; } mid_elem = low_elem; low_elem++; /* this cur_elem exhausted, too */ } if (high_elem < low_elem) { /* Caller needs to perform "beyond end" array advancement */ *set_elem_result = 1; return high_elem; } } else { high_elem = array->cur_elem - 1; /* old cur_elem exhausted */ /* Compare prospective new cur_elem (also the new upper bound) */ if (high_elem >= low_elem) { arrdatum = array->elem_values[high_elem]; result = _bt_compare_array_skey(orderproc, tupdatum, tupnull, arrdatum, cur); if (result >= 0) { /* Optimistic comparison optimization worked out */ *set_elem_result = result; return high_elem; } mid_elem = high_elem; high_elem--; /* this cur_elem exhausted, too */ } if (high_elem < low_elem) { /* Caller needs to perform "beyond end" array advancement */ *set_elem_result = -1; return low_elem; } } } while (high_elem > low_elem) { mid_elem = low_elem + ((high_elem - low_elem) / 2); arrdatum = array->elem_values[mid_elem]; result = _bt_compare_array_skey(orderproc, tupdatum, tupnull, arrdatum, cur); if (result == 0) { /* * It's safe to quit as soon as we see an equal array element. * This often saves an extra comparison or two... */ low_elem = mid_elem; break; } if (result > 0) low_elem = mid_elem + 1; else high_elem = mid_elem; } /* * ...but our caller also cares about how its searched-for tuple datum * compares to the low_elem datum. Must always set *set_elem_result with * the result of that comparison specifically. */ if (low_elem != mid_elem) result = _bt_compare_array_skey(orderproc, tupdatum, tupnull, array->elem_values[low_elem], cur); *set_elem_result = result; return low_elem; } /* * _bt_binsrch_skiparray_skey() -- "Binary search" within a skip array * * Does not return an index into the array, since skip arrays don't really * contain elements (they generate their array elements procedurally instead). * Our interface matches that of _bt_binsrch_array_skey in every other way. * * Sets *set_elem_result just like _bt_binsrch_array_skey would with a true * array. The value 0 indicates that tupdatum/tupnull is within the range of * the skip array. We return -1 when tupdatum/tupnull is lower that any value * within the range of the array, and 1 when it is higher than every value. * Caller should pass *set_elem_result to _bt_skiparray_set_element to advance * the array. * * cur_elem_trig indicates if array advancement was triggered by this array's * scan key. We use this to optimize-away comparisons that are known by our * caller to be unnecessary from context, just like _bt_binsrch_array_skey. */ static void _bt_binsrch_skiparray_skey(bool cur_elem_trig, ScanDirection dir, Datum tupdatum, bool tupnull, BTArrayKeyInfo *array, ScanKey cur, int32 *set_elem_result) { Assert(cur->sk_flags & SK_BT_SKIP); Assert(cur->sk_flags & SK_SEARCHARRAY); Assert(cur->sk_flags & SK_BT_REQFWD); Assert(array->num_elems == -1); Assert(!ScanDirectionIsNoMovement(dir)); if (array->null_elem) { Assert(!array->low_compare && !array->high_compare); *set_elem_result = 0; return; } if (tupnull) /* NULL tupdatum */ { if (cur->sk_flags & SK_BT_NULLS_FIRST) *set_elem_result = -1; /* NULL "<" NOT_NULL */ else *set_elem_result = 1; /* NULL ">" NOT_NULL */ return; } /* * Array inequalities determine whether tupdatum is within the range of * caller's skip array */ *set_elem_result = 0; if (ScanDirectionIsForward(dir)) { /* * Evaluate low_compare first (unless cur_elem_trig tells us that it * cannot possibly fail to be satisfied), then evaluate high_compare */ if (!cur_elem_trig && array->low_compare && !DatumGetBool(FunctionCall2Coll(&array->low_compare->sk_func, array->low_compare->sk_collation, tupdatum, array->low_compare->sk_argument))) *set_elem_result = -1; else if (array->high_compare && !DatumGetBool(FunctionCall2Coll(&array->high_compare->sk_func, array->high_compare->sk_collation, tupdatum, array->high_compare->sk_argument))) *set_elem_result = 1; } else { /* * Evaluate high_compare first (unless cur_elem_trig tells us that it * cannot possibly fail to be satisfied), then evaluate low_compare */ if (!cur_elem_trig && array->high_compare && !DatumGetBool(FunctionCall2Coll(&array->high_compare->sk_func, array->high_compare->sk_collation, tupdatum, array->high_compare->sk_argument))) *set_elem_result = 1; else if (array->low_compare && !DatumGetBool(FunctionCall2Coll(&array->low_compare->sk_func, array->low_compare->sk_collation, tupdatum, array->low_compare->sk_argument))) *set_elem_result = -1; } /* * Assert that any keys that were assumed to be satisfied already (due to * caller passing cur_elem_trig=true) really are satisfied as expected */ #ifdef USE_ASSERT_CHECKING if (cur_elem_trig) { if (ScanDirectionIsForward(dir) && array->low_compare) Assert(DatumGetBool(FunctionCall2Coll(&array->low_compare->sk_func, array->low_compare->sk_collation, tupdatum, array->low_compare->sk_argument))); if (ScanDirectionIsBackward(dir) && array->high_compare) Assert(DatumGetBool(FunctionCall2Coll(&array->high_compare->sk_func, array->high_compare->sk_collation, tupdatum, array->high_compare->sk_argument))); } #endif } /* * _bt_skiparray_set_element() -- Set skip array scan key's sk_argument * * Caller passes set_elem_result returned by _bt_binsrch_skiparray_skey for * caller's tupdatum/tupnull. * * We copy tupdatum/tupnull into skey's sk_argument iff set_elem_result == 0. * Otherwise, we set skey to either the lowest or highest value that's within * the range of caller's skip array (whichever is the best available match to * tupdatum/tupnull that is still within the range of the skip array according * to _bt_binsrch_skiparray_skey/set_elem_result). */ static void _bt_skiparray_set_element(Relation rel, ScanKey skey, BTArrayKeyInfo *array, int32 set_elem_result, Datum tupdatum, bool tupnull) { Assert(skey->sk_flags & SK_BT_SKIP); Assert(skey->sk_flags & SK_SEARCHARRAY); if (set_elem_result) { /* tupdatum/tupnull is out of the range of the skip array */ Assert(!array->null_elem); _bt_array_set_low_or_high(rel, skey, array, set_elem_result < 0); return; } /* Advance skip array to tupdatum (or tupnull) value */ if (unlikely(tupnull)) { _bt_skiparray_set_isnull(rel, skey, array); return; } /* Free memory previously allocated for sk_argument if needed */ if (!array->attbyval && skey->sk_argument) pfree(DatumGetPointer(skey->sk_argument)); /* tupdatum becomes new sk_argument/new current element */ skey->sk_flags &= ~(SK_SEARCHNULL | SK_ISNULL | SK_BT_MINVAL | SK_BT_MAXVAL | SK_BT_NEXT | SK_BT_PRIOR); skey->sk_argument = datumCopy(tupdatum, array->attbyval, array->attlen); } /* * _bt_skiparray_set_isnull() -- set skip array scan key to NULL */ static void _bt_skiparray_set_isnull(Relation rel, ScanKey skey, BTArrayKeyInfo *array) { Assert(skey->sk_flags & SK_BT_SKIP); Assert(skey->sk_flags & SK_SEARCHARRAY); Assert(array->null_elem && !array->low_compare && !array->high_compare); /* Free memory previously allocated for sk_argument if needed */ if (!array->attbyval && skey->sk_argument) pfree(DatumGetPointer(skey->sk_argument)); /* NULL becomes new sk_argument/new current element */ skey->sk_argument = (Datum) 0; skey->sk_flags &= ~(SK_BT_MINVAL | SK_BT_MAXVAL | SK_BT_NEXT | SK_BT_PRIOR); skey->sk_flags |= (SK_SEARCHNULL | SK_ISNULL); } /* * _bt_start_array_keys() -- Initialize array keys at start of a scan * * Set up the cur_elem counters and fill in the first sk_argument value for * each array scankey. */ void _bt_start_array_keys(IndexScanDesc scan, ScanDirection dir) { Relation rel = scan->indexRelation; BTScanOpaque so = (BTScanOpaque) scan->opaque; Assert(so->numArrayKeys); Assert(so->qual_ok); for (int i = 0; i < so->numArrayKeys; i++) { BTArrayKeyInfo *array = &so->arrayKeys[i]; ScanKey skey = &so->keyData[array->scan_key]; Assert(skey->sk_flags & SK_SEARCHARRAY); _bt_array_set_low_or_high(rel, skey, array, ScanDirectionIsForward(dir)); } so->scanBehind = so->oppositeDirCheck = false; /* reset */ } /* * _bt_array_set_low_or_high() -- Set array scan key to lowest/highest element * * Caller also passes associated scan key, which will have its argument set to * the lowest/highest array value in passing. */ static void _bt_array_set_low_or_high(Relation rel, ScanKey skey, BTArrayKeyInfo *array, bool low_not_high) { Assert(skey->sk_flags & SK_SEARCHARRAY); if (array->num_elems != -1) { /* set low or high element for SAOP array */ int set_elem = 0; Assert(!(skey->sk_flags & SK_BT_SKIP)); if (!low_not_high) set_elem = array->num_elems - 1; /* * Just copy over array datum (only skip arrays require freeing and * allocating memory for sk_argument) */ array->cur_elem = set_elem; skey->sk_argument = array->elem_values[set_elem]; return; } /* set low or high element for skip array */ Assert(skey->sk_flags & SK_BT_SKIP); Assert(array->num_elems == -1); /* Free memory previously allocated for sk_argument if needed */ if (!array->attbyval && skey->sk_argument) pfree(DatumGetPointer(skey->sk_argument)); /* Reset flags */ skey->sk_argument = (Datum) 0; skey->sk_flags &= ~(SK_SEARCHNULL | SK_ISNULL | SK_BT_MINVAL | SK_BT_MAXVAL | SK_BT_NEXT | SK_BT_PRIOR); if (array->null_elem && (low_not_high == ((skey->sk_flags & SK_BT_NULLS_FIRST) != 0))) { /* Requested element (either lowest or highest) has the value NULL */ skey->sk_flags |= (SK_SEARCHNULL | SK_ISNULL); } else if (low_not_high) { /* Setting array to lowest element (according to low_compare) */ skey->sk_flags |= SK_BT_MINVAL; } else { /* Setting array to highest element (according to high_compare) */ skey->sk_flags |= SK_BT_MAXVAL; } } /* * _bt_array_decrement() -- decrement array scan key's sk_argument * * Return value indicates whether caller's array was successfully decremented. * Cannot decrement an array whose current element is already the first one. */ static bool _bt_array_decrement(Relation rel, ScanKey skey, BTArrayKeyInfo *array) { bool uflow = false; Datum dec_sk_argument; Assert(skey->sk_flags & SK_SEARCHARRAY); Assert(!(skey->sk_flags & (SK_BT_MAXVAL | SK_BT_NEXT | SK_BT_PRIOR))); /* SAOP array? */ if (array->num_elems != -1) { Assert(!(skey->sk_flags & (SK_BT_SKIP | SK_BT_MINVAL | SK_BT_MAXVAL))); if (array->cur_elem > 0) { /* * Just decrement current element, and assign its datum to skey * (only skip arrays need us to free existing sk_argument memory) */ array->cur_elem--; skey->sk_argument = array->elem_values[array->cur_elem]; /* Successfully decremented array */ return true; } /* Cannot decrement to before first array element */ return false; } /* Nope, this is a skip array */ Assert(skey->sk_flags & SK_BT_SKIP); /* * The sentinel value that represents the minimum value within the range * of a skip array (often just -inf) is never decrementable */ if (skey->sk_flags & SK_BT_MINVAL) return false; /* * When the current array element is NULL, and the lowest sorting value in * the index is also NULL, we cannot decrement before first array element */ if ((skey->sk_flags & SK_ISNULL) && (skey->sk_flags & SK_BT_NULLS_FIRST)) return false; /* * Opclasses without skip support "decrement" the scan key's current * element by setting the PRIOR flag. The true prior value is determined * by repositioning to the last index tuple < existing sk_argument/current * array element. Note that this works in the usual way when the scan key * is already marked ISNULL (i.e. when the current element is NULL). */ if (!array->sksup) { /* Successfully "decremented" array */ skey->sk_flags |= SK_BT_PRIOR; return true; } /* * Opclasses with skip support directly decrement sk_argument */ if (skey->sk_flags & SK_ISNULL) { Assert(!(skey->sk_flags & SK_BT_NULLS_FIRST)); /* * Existing sk_argument/array element is NULL (for an IS NULL qual). * * "Decrement" from NULL to the high_elem value provided by opclass * skip support routine. */ skey->sk_flags &= ~(SK_SEARCHNULL | SK_ISNULL); skey->sk_argument = datumCopy(array->sksup->high_elem, array->attbyval, array->attlen); return true; } /* * Ask opclass support routine to provide decremented copy of existing * non-NULL sk_argument */ dec_sk_argument = array->sksup->decrement(rel, skey->sk_argument, &uflow); if (unlikely(uflow)) { /* dec_sk_argument has undefined value (so no pfree) */ if (array->null_elem && (skey->sk_flags & SK_BT_NULLS_FIRST)) { _bt_skiparray_set_isnull(rel, skey, array); /* Successfully "decremented" array to NULL */ return true; } /* Cannot decrement to before first array element */ return false; } /* * Successfully decremented sk_argument to a non-NULL value. Make sure * that the decremented value is still within the range of the array. */ if (array->low_compare && !DatumGetBool(FunctionCall2Coll(&array->low_compare->sk_func, array->low_compare->sk_collation, dec_sk_argument, array->low_compare->sk_argument))) { /* Keep existing sk_argument after all */ if (!array->attbyval) pfree(DatumGetPointer(dec_sk_argument)); /* Cannot decrement to before first array element */ return false; } /* Accept value returned by opclass decrement callback */ if (!array->attbyval && skey->sk_argument) pfree(DatumGetPointer(skey->sk_argument)); skey->sk_argument = dec_sk_argument; /* Successfully decremented array */ return true; } /* * _bt_array_increment() -- increment array scan key's sk_argument * * Return value indicates whether caller's array was successfully incremented. * Cannot increment an array whose current element is already the final one. */ static bool _bt_array_increment(Relation rel, ScanKey skey, BTArrayKeyInfo *array) { bool oflow = false; Datum inc_sk_argument; Assert(skey->sk_flags & SK_SEARCHARRAY); Assert(!(skey->sk_flags & (SK_BT_MINVAL | SK_BT_NEXT | SK_BT_PRIOR))); /* SAOP array? */ if (array->num_elems != -1) { Assert(!(skey->sk_flags & (SK_BT_SKIP | SK_BT_MINVAL | SK_BT_MAXVAL))); if (array->cur_elem < array->num_elems - 1) { /* * Just increment current element, and assign its datum to skey * (only skip arrays need us to free existing sk_argument memory) */ array->cur_elem++; skey->sk_argument = array->elem_values[array->cur_elem]; /* Successfully incremented array */ return true; } /* Cannot increment past final array element */ return false; } /* Nope, this is a skip array */ Assert(skey->sk_flags & SK_BT_SKIP); /* * The sentinel value that represents the maximum value within the range * of a skip array (often just +inf) is never incrementable */ if (skey->sk_flags & SK_BT_MAXVAL) return false; /* * When the current array element is NULL, and the highest sorting value * in the index is also NULL, we cannot increment past the final element */ if ((skey->sk_flags & SK_ISNULL) && !(skey->sk_flags & SK_BT_NULLS_FIRST)) return false; /* * Opclasses without skip support "increment" the scan key's current * element by setting the NEXT flag. The true next value is determined by * repositioning to the first index tuple > existing sk_argument/current * array element. Note that this works in the usual way when the scan key * is already marked ISNULL (i.e. when the current element is NULL). */ if (!array->sksup) { /* Successfully "incremented" array */ skey->sk_flags |= SK_BT_NEXT; return true; } /* * Opclasses with skip support directly increment sk_argument */ if (skey->sk_flags & SK_ISNULL) { Assert(skey->sk_flags & SK_BT_NULLS_FIRST); /* * Existing sk_argument/array element is NULL (for an IS NULL qual). * * "Increment" from NULL to the low_elem value provided by opclass * skip support routine. */ skey->sk_flags &= ~(SK_SEARCHNULL | SK_ISNULL); skey->sk_argument = datumCopy(array->sksup->low_elem, array->attbyval, array->attlen); return true; } /* * Ask opclass support routine to provide incremented copy of existing * non-NULL sk_argument */ inc_sk_argument = array->sksup->increment(rel, skey->sk_argument, &oflow); if (unlikely(oflow)) { /* inc_sk_argument has undefined value (so no pfree) */ if (array->null_elem && !(skey->sk_flags & SK_BT_NULLS_FIRST)) { _bt_skiparray_set_isnull(rel, skey, array); /* Successfully "incremented" array to NULL */ return true; } /* Cannot increment past final array element */ return false; } /* * Successfully incremented sk_argument to a non-NULL value. Make sure * that the incremented value is still within the range of the array. */ if (array->high_compare && !DatumGetBool(FunctionCall2Coll(&array->high_compare->sk_func, array->high_compare->sk_collation, inc_sk_argument, array->high_compare->sk_argument))) { /* Keep existing sk_argument after all */ if (!array->attbyval) pfree(DatumGetPointer(inc_sk_argument)); /* Cannot increment past final array element */ return false; } /* Accept value returned by opclass increment callback */ if (!array->attbyval && skey->sk_argument) pfree(DatumGetPointer(skey->sk_argument)); skey->sk_argument = inc_sk_argument; /* Successfully incremented array */ return true; } /* * _bt_advance_array_keys_increment() -- Advance to next set of array elements * * Advances the array keys by a single increment in the current scan * direction. When there are multiple array keys this can roll over from the * lowest order array to higher order arrays. * * Returns true if there is another set of values to consider, false if not. * On true result, the scankeys are initialized with the next set of values. * On false result, the scankeys stay the same, and the array keys are not * advanced (every array remains at its final element for scan direction). */ static bool _bt_advance_array_keys_increment(IndexScanDesc scan, ScanDirection dir, bool *skip_array_set) { Relation rel = scan->indexRelation; BTScanOpaque so = (BTScanOpaque) scan->opaque; /* * We must advance the last array key most quickly, since it will * correspond to the lowest-order index column among the available * qualifications */ for (int i = so->numArrayKeys - 1; i >= 0; i--) { BTArrayKeyInfo *array = &so->arrayKeys[i]; ScanKey skey = &so->keyData[array->scan_key]; if (array->num_elems == -1) *skip_array_set = true; if (ScanDirectionIsForward(dir)) { if (_bt_array_increment(rel, skey, array)) return true; } else { if (_bt_array_decrement(rel, skey, array)) return true; } /* * Couldn't increment (or decrement) array. Handle array roll over. * * Start over at the array's lowest sorting value (or its highest * value, for backward scans)... */ _bt_array_set_low_or_high(rel, skey, array, ScanDirectionIsForward(dir)); /* ...then increment (or decrement) next most significant array */ } /* * The array keys are now exhausted. * * Restore the array keys to the state they were in immediately before we * were called. This ensures that the arrays only ever ratchet in the * current scan direction. * * Without this, scans could overlook matching tuples when the scan * direction gets reversed just before btgettuple runs out of items to * return, but just after _bt_readpage prepares all the items from the * scan's final page in so->currPos. When we're on the final page it is * typical for so->currPos to get invalidated once btgettuple finally * returns false, which'll effectively invalidate the scan's array keys. * That hasn't happened yet, though -- and in general it may never happen. */ _bt_start_array_keys(scan, -dir); return false; } /* * _bt_rewind_nonrequired_arrays() -- Rewind SAOP arrays not marked required * * Called when _bt_advance_array_keys decides to start a new primitive index * scan on the basis of the current scan position being before the position * that _bt_first is capable of repositioning the scan to by applying an * inequality operator required in the opposite-to-scan direction only. * * Although equality strategy scan keys (for both arrays and non-arrays alike) * are either marked required in both directions or in neither direction, * there is a sense in which non-required arrays behave like required arrays. * With a qual such as "WHERE a IN (100, 200) AND b >= 3 AND c IN (5, 6, 7)", * the scan key on "c" is non-required, but nevertheless enables positioning * the scan at the first tuple >= "(100, 3, 5)" on the leaf level during the * first descent of the tree by _bt_first. Later on, there could also be a * second descent, that places the scan right before tuples >= "(200, 3, 5)". * _bt_first must never be allowed to build an insertion scan key whose "c" * entry is set to a value other than 5, the "c" array's first element/value. * (Actually, it's the first in the current scan direction. This example uses * a forward scan.) * * Calling here resets the array scan key elements for the scan's non-required * arrays. This is strictly necessary for correctness in a subset of cases * involving "required in opposite direction"-triggered primitive index scans. * Not all callers are at risk of _bt_first using a non-required array like * this, but advancement always resets the arrays when another primitive scan * is scheduled, just to keep things simple. Array advancement even makes * sure to reset non-required arrays during scans that have no inequalities. * (Advancement still won't call here when there are no inequalities, though * that's just because it's all handled indirectly instead.) * * Note: _bt_verify_arrays_bt_first is called by an assertion to enforce that * everybody got this right. * * Note: In practice almost all SAOP arrays are marked required during * preprocessing (if necessary by generating skip arrays). It is hardly ever * truly necessary to call here, but consistently doing so is simpler. */ static void _bt_rewind_nonrequired_arrays(IndexScanDesc scan, ScanDirection dir) { Relation rel = scan->indexRelation; BTScanOpaque so = (BTScanOpaque) scan->opaque; int arrayidx = 0; for (int ikey = 0; ikey < so->numberOfKeys; ikey++) { ScanKey cur = so->keyData + ikey; BTArrayKeyInfo *array = NULL; if (!(cur->sk_flags & SK_SEARCHARRAY) || cur->sk_strategy != BTEqualStrategyNumber) continue; array = &so->arrayKeys[arrayidx++]; Assert(array->scan_key == ikey); if ((cur->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD))) continue; Assert(array->num_elems != -1); /* No non-required skip arrays */ _bt_array_set_low_or_high(rel, cur, array, ScanDirectionIsForward(dir)); } } /* * _bt_tuple_before_array_skeys() -- too early to advance required arrays? * * We always compare the tuple using the current array keys (which we assume * are already set in so->keyData[]). readpagetup indicates if tuple is the * scan's current _bt_readpage-wise tuple. * * readpagetup callers must only call here when _bt_check_compare already set * continuescan=false. We help these callers deal with _bt_check_compare's * inability to distinguish between the < and > cases (it uses equality * operator scan keys, whereas we use 3-way ORDER procs). These callers pass * a _bt_check_compare-set sktrig value that indicates which scan key * triggered the call (!readpagetup callers just pass us sktrig=0 instead). * This information allows us to avoid wastefully checking earlier scan keys * that were already deemed to have been satisfied inside _bt_check_compare. * * Returns false when caller's tuple is >= the current required equality scan * keys (or <=, in the case of backwards scans). This happens to readpagetup * callers when the scan has reached the point of needing its array keys * advanced; caller will need to advance required and non-required arrays at * scan key offsets >= sktrig, plus scan keys < sktrig iff sktrig rolls over. * (When we return false to readpagetup callers, tuple can only be == current * required equality scan keys when caller's sktrig indicates that the arrays * need to be advanced due to an unsatisfied required inequality key trigger.) * * Returns true when caller passes a tuple that is < the current set of * equality keys for the most significant non-equal required scan key/column * (or > the keys, during backwards scans). This happens to readpagetup * callers when tuple is still before the start of matches for the scan's * required equality strategy scan keys. (sktrig can't have indicated that an * inequality strategy scan key wasn't satisfied in _bt_check_compare when we * return true. In fact, we automatically return false when passed such an * inequality sktrig by readpagetup callers -- _bt_check_compare's initial * continuescan=false doesn't really need to be confirmed here by us.) * * !readpagetup callers optionally pass us *scanBehind, which tracks whether * any missing truncated attributes might have affected array advancement * (compared to what would happen if it was shown the first non-pivot tuple on * the page to the right of caller's finaltup/high key tuple instead). It's * only possible that we'll set *scanBehind to true when caller passes us a * pivot tuple (with truncated -inf attributes) that we return false for. */ static bool _bt_tuple_before_array_skeys(IndexScanDesc scan, ScanDirection dir, IndexTuple tuple, TupleDesc tupdesc, int tupnatts, bool readpagetup, int sktrig, bool *scanBehind) { BTScanOpaque so = (BTScanOpaque) scan->opaque; Assert(so->numArrayKeys); Assert(so->numberOfKeys); Assert(sktrig == 0 || readpagetup); Assert(!readpagetup || scanBehind == NULL); if (scanBehind) *scanBehind = false; for (int ikey = sktrig; ikey < so->numberOfKeys; ikey++) { ScanKey cur = so->keyData + ikey; Datum tupdatum; bool tupnull; int32 result; /* readpagetup calls require one ORDER proc comparison (at most) */ Assert(!readpagetup || ikey == sktrig); /* * Once we reach a non-required scan key, we're completely done. * * Note: we deliberately don't consider the scan direction here. * _bt_advance_array_keys caller requires that we track *scanBehind * without concern for scan direction. */ if ((cur->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)) == 0) { Assert(!readpagetup); Assert(ikey > sktrig || ikey == 0); return false; } if (cur->sk_attno > tupnatts) { Assert(!readpagetup); /* * When we reach a high key's truncated attribute, assume that the * tuple attribute's value is >= the scan's equality constraint * scan keys (but set *scanBehind to let interested callers know * that a truncated attribute might have affected our answer). */ if (scanBehind) *scanBehind = true; return false; } /* * Deal with inequality strategy scan keys that _bt_check_compare set * continuescan=false for */ if (cur->sk_strategy != BTEqualStrategyNumber) { /* * When _bt_check_compare indicated that a required inequality * scan key wasn't satisfied, there's no need to verify anything; * caller always calls _bt_advance_array_keys with this sktrig. */ if (readpagetup) return false; /* * Otherwise we can't give up, since we must check all required * scan keys (required in either direction) in order to correctly * track *scanBehind for caller */ continue; } tupdatum = index_getattr(tuple, cur->sk_attno, tupdesc, &tupnull); if (likely(!(cur->sk_flags & (SK_BT_MINVAL | SK_BT_MAXVAL)))) { /* Scankey has a valid/comparable sk_argument value */ result = _bt_compare_array_skey(&so->orderProcs[ikey], tupdatum, tupnull, cur->sk_argument, cur); if (result == 0) { /* * Interpret result in a way that takes NEXT/PRIOR into * account */ if (cur->sk_flags & SK_BT_NEXT) result = -1; else if (cur->sk_flags & SK_BT_PRIOR) result = 1; Assert(result == 0 || (cur->sk_flags & SK_BT_SKIP)); } } else { BTArrayKeyInfo *array = NULL; /* * Current array element/array = scan key value is a sentinel * value that represents the lowest (or highest) possible value * that's still within the range of the array. * * Like _bt_first, we only see MINVAL keys during forwards scans * (and similarly only see MAXVAL keys during backwards scans). * Even if the scan's direction changes, we'll stop at some higher * order key before we can ever reach any MAXVAL (or MINVAL) keys. * (However, unlike _bt_first we _can_ get to keys marked either * NEXT or PRIOR, regardless of the scan's current direction.) */ Assert(ScanDirectionIsForward(dir) ? !(cur->sk_flags & SK_BT_MAXVAL) : !(cur->sk_flags & SK_BT_MINVAL)); /* * There are no valid sk_argument values in MINVAL/MAXVAL keys. * Check if tupdatum is within the range of skip array instead. */ for (int arrayidx = 0; arrayidx < so->numArrayKeys; arrayidx++) { array = &so->arrayKeys[arrayidx]; if (array->scan_key == ikey) break; } _bt_binsrch_skiparray_skey(false, dir, tupdatum, tupnull, array, cur, &result); if (result == 0) { /* * tupdatum satisfies both low_compare and high_compare, so * it's time to advance the array keys. * * Note: It's possible that the skip array will "advance" from * its MINVAL (or MAXVAL) representation to an alternative, * logically equivalent representation of the same value: a * representation where the = key gets a valid datum in its * sk_argument. This is only possible when low_compare uses * the >= strategy (or high_compare uses the <= strategy). */ return false; } } /* * Does this comparison indicate that caller must _not_ advance the * scan's arrays just yet? */ if ((ScanDirectionIsForward(dir) && result < 0) || (ScanDirectionIsBackward(dir) && result > 0)) return true; /* * Does this comparison indicate that caller should now advance the * scan's arrays? (Must be if we get here during a readpagetup call.) */ if (readpagetup || result != 0) { Assert(result != 0); return false; } /* * Inconclusive -- need to check later scan keys, too. * * This must be a finaltup precheck, or a call made from an assertion. */ Assert(result == 0); } Assert(!readpagetup); return false; } /* * _bt_start_prim_scan() -- start scheduled primitive index scan? * * Returns true if _bt_checkkeys scheduled another primitive index scan, just * as the last one ended. Otherwise returns false, indicating that the array * keys are now fully exhausted. * * Only call here during scans with one or more equality type array scan keys, * after _bt_first or _bt_next return false. */ bool _bt_start_prim_scan(IndexScanDesc scan, ScanDirection dir) { BTScanOpaque so = (BTScanOpaque) scan->opaque; Assert(so->numArrayKeys); so->scanBehind = so->oppositeDirCheck = false; /* reset */ /* * Array keys are advanced within _bt_checkkeys when the scan reaches the * leaf level (more precisely, they're advanced when the scan reaches the * end of each distinct set of array elements). This process avoids * repeat access to leaf pages (across multiple primitive index scans) by * advancing the scan's array keys when it allows the primitive index scan * to find nearby matching tuples (or when it eliminates ranges of array * key space that can't possibly be satisfied by any index tuple). * * _bt_checkkeys sets a simple flag variable to schedule another primitive * index scan. The flag tells us what to do. * * We cannot rely on _bt_first always reaching _bt_checkkeys. There are * various cases where that won't happen. For example, if the index is * completely empty, then _bt_first won't call _bt_readpage/_bt_checkkeys. * We also don't expect a call to _bt_checkkeys during searches for a * non-existent value that happens to be lower/higher than any existing * value in the index. * * We don't require special handling for these cases -- we don't need to * be explicitly instructed to _not_ perform another primitive index scan. * It's up to code under the control of _bt_first to always set the flag * when another primitive index scan will be required. * * This works correctly, even with the tricky cases listed above, which * all involve access to leaf pages "near the boundaries of the key space" * (whether it's from a leftmost/rightmost page, or an imaginary empty * leaf root page). If _bt_checkkeys cannot be reached by a primitive * index scan for one set of array keys, then it also won't be reached for * any later set ("later" in terms of the direction that we scan the index * and advance the arrays). The array keys won't have advanced in these * cases, but that's the correct behavior (even _bt_advance_array_keys * won't always advance the arrays at the point they become "exhausted"). */ if (so->needPrimScan) { Assert(_bt_verify_arrays_bt_first(scan, dir)); /* * Flag was set -- must call _bt_first again, which will reset the * scan's needPrimScan flag */ return true; } /* The top-level index scan ran out of tuples in this scan direction */ if (scan->parallel_scan != NULL) _bt_parallel_done(scan); return false; } /* * _bt_advance_array_keys() -- Advance array elements using a tuple * * The scan always gets a new qual as a consequence of calling here (except * when we determine that the top-level scan has run out of matching tuples). * All later _bt_check_compare calls also use the same new qual that was first * used here (at least until the next call here advances the keys once again). * It's convenient to structure _bt_check_compare rechecks of caller's tuple * (using the new qual) as one the steps of advancing the scan's array keys, * so this function works as a wrapper around _bt_check_compare. * * Like _bt_check_compare, we'll set pstate.continuescan on behalf of the * caller, and return a boolean indicating if caller's tuple satisfies the * scan's new qual. But unlike _bt_check_compare, we set so->needPrimScan * when we set continuescan=false, indicating if a new primitive index scan * has been scheduled (otherwise, the top-level scan has run out of tuples in * the current scan direction). * * Caller must use _bt_tuple_before_array_skeys to determine if the current * place in the scan is >= the current array keys _before_ calling here. * We're responsible for ensuring that caller's tuple is <= the newly advanced * required array keys once we return. We try to find an exact match, but * failing that we'll advance the array keys to whatever set of array elements * comes next in the key space for the current scan direction. Required array * keys "ratchet forwards" (or backwards). They can only advance as the scan * itself advances through the index/key space. * * (The rules are the same for backwards scans, except that the operators are * flipped: just replace the precondition's >= operator with a <=, and the * postcondition's <= operator with a >=. In other words, just swap the * precondition with the postcondition.) * * We also deal with "advancing" non-required arrays here (or arrays that are * treated as non-required for the duration of a _bt_readpage call). Callers * whose sktrig scan key is non-required specify sktrig_required=false. These * calls are the only exception to the general rule about always advancing the * required array keys (the scan may not even have a required array). These * callers should just pass a NULL pstate (since there is never any question * of stopping the scan). No call to _bt_tuple_before_array_skeys is required * ahead of these calls (it's already clear that any required scan keys must * be satisfied by caller's tuple). * * Note that we deal with non-array required equality strategy scan keys as * degenerate single element arrays here. Obviously, they can never really * advance in the way that real arrays can, but they must still affect how we * advance real array scan keys (exactly like true array equality scan keys). * We have to keep around a 3-way ORDER proc for these (using the "=" operator * won't do), since in general whether the tuple is < or > _any_ unsatisfied * required equality key influences how the scan's real arrays must advance. * * Note also that we may sometimes need to advance the array keys when the * existing required array keys (and other required equality keys) are already * an exact match for every corresponding value from caller's tuple. We must * do this for inequalities that _bt_check_compare set continuescan=false for. * They'll advance the array keys here, just like any other scan key that * _bt_check_compare stops on. (This can even happen _after_ we advance the * array keys, in which case we'll advance the array keys a second time. That * way _bt_checkkeys caller always has its required arrays advance to the * maximum possible extent that its tuple will allow.) */ static bool _bt_advance_array_keys(IndexScanDesc scan, BTReadPageState *pstate, IndexTuple tuple, int tupnatts, TupleDesc tupdesc, int sktrig, bool sktrig_required) { BTScanOpaque so = (BTScanOpaque) scan->opaque; Relation rel = scan->indexRelation; ScanDirection dir = so->currPos.dir; int arrayidx = 0; bool beyond_end_advance = false, skip_array_advanced = false, has_required_opposite_direction_only = false, all_required_satisfied = true, all_satisfied = true; Assert(!so->needPrimScan && !so->scanBehind && !so->oppositeDirCheck); Assert(_bt_verify_keys_with_arraykeys(scan)); if (sktrig_required) { /* * Precondition array state assertion */ Assert(!_bt_tuple_before_array_skeys(scan, dir, tuple, tupdesc, tupnatts, false, 0, NULL)); /* * Once we return we'll have a new set of required array keys, so * reset state used by "look ahead" optimization */ pstate->rechecks = 0; pstate->targetdistance = 0; } else if (sktrig < so->numberOfKeys - 1 && !(so->keyData[so->numberOfKeys - 1].sk_flags & SK_SEARCHARRAY)) { int least_sign_ikey = so->numberOfKeys - 1; bool continuescan; /* * Optimization: perform a precheck of the least significant key * during !sktrig_required calls when it isn't already our sktrig * (provided the precheck key is not itself an array). * * When the precheck works out we'll avoid an expensive binary search * of sktrig's array (plus any other arrays before least_sign_ikey). */ Assert(so->keyData[sktrig].sk_flags & SK_SEARCHARRAY); if (!_bt_check_compare(scan, dir, tuple, tupnatts, tupdesc, false, false, &continuescan, &least_sign_ikey)) return false; } for (int ikey = 0; ikey < so->numberOfKeys; ikey++) { ScanKey cur = so->keyData + ikey; BTArrayKeyInfo *array = NULL; Datum tupdatum; bool required = false, required_opposite_direction_only = false, tupnull; int32 result; int set_elem = 0; if (cur->sk_strategy == BTEqualStrategyNumber) { /* Manage array state */ if (cur->sk_flags & SK_SEARCHARRAY) { array = &so->arrayKeys[arrayidx++]; Assert(array->scan_key == ikey); } } else { /* * Are any inequalities required in the opposite direction only * present here? */ if (((ScanDirectionIsForward(dir) && (cur->sk_flags & (SK_BT_REQBKWD))) || (ScanDirectionIsBackward(dir) && (cur->sk_flags & (SK_BT_REQFWD))))) has_required_opposite_direction_only = required_opposite_direction_only = true; } /* Optimization: skip over known-satisfied scan keys */ if (ikey < sktrig) continue; if (cur->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)) { required = true; if (cur->sk_attno > tupnatts) { /* Set this just like _bt_tuple_before_array_skeys */ Assert(sktrig < ikey); so->scanBehind = true; } } /* * Handle a required non-array scan key that the initial call to * _bt_check_compare indicated triggered array advancement, if any. * * The non-array scan key's strategy will be <, <=, or = during a * forwards scan (or any one of =, >=, or > during a backwards scan). * It follows that the corresponding tuple attribute's value must now * be either > or >= the scan key value (for backwards scans it must * be either < or <= that value). * * If this is a required equality strategy scan key, this is just an * optimization; _bt_tuple_before_array_skeys already confirmed that * this scan key places us ahead of caller's tuple. There's no need * to repeat that work now. (The same underlying principle also gets * applied by the cur_elem_trig optimization used to speed up searches * for the next array element.) * * If this is a required inequality strategy scan key, we _must_ rely * on _bt_check_compare like this; we aren't capable of directly * evaluating required inequality strategy scan keys here, on our own. */ if (ikey == sktrig && !array) { Assert(sktrig_required && required && all_required_satisfied); /* Use "beyond end" advancement. See below for an explanation. */ beyond_end_advance = true; all_satisfied = all_required_satisfied = false; continue; } /* * Nothing more for us to do with an inequality strategy scan key that * wasn't the one that _bt_check_compare stopped on, though. * * Note: if our later call to _bt_check_compare (to recheck caller's * tuple) sets continuescan=false due to finding this same inequality * unsatisfied (possible when it's required in the scan direction), * we'll deal with it via a recursive "second pass" call. */ else if (cur->sk_strategy != BTEqualStrategyNumber) continue; /* * Nothing for us to do with an equality strategy scan key that isn't * marked required, either -- unless it's a non-required array */ else if (!required && !array) continue; /* * Here we perform steps for all array scan keys after a required * array scan key whose binary search triggered "beyond end of array * element" array advancement due to encountering a tuple attribute * value > the closest matching array key (or < for backwards scans). */ if (beyond_end_advance) { if (array) _bt_array_set_low_or_high(rel, cur, array, ScanDirectionIsBackward(dir)); continue; } /* * Here we perform steps for all array scan keys after a required * array scan key whose tuple attribute was < the closest matching * array key when we dealt with it (or > for backwards scans). * * This earlier required array key already puts us ahead of caller's * tuple in the key space (for the current scan direction). We must * make sure that subsequent lower-order array keys do not put us too * far ahead (ahead of tuples that have yet to be seen by our caller). * For example, when a tuple "(a, b) = (42, 5)" advances the array * keys on "a" from 40 to 45, we must also set "b" to whatever the * first array element for "b" is. It would be wrong to allow "b" to * be set based on the tuple value. * * Perform the same steps with truncated high key attributes. You can * think of this as a "binary search" for the element closest to the * value -inf. Again, the arrays must never get ahead of the scan. */ if (!all_required_satisfied || cur->sk_attno > tupnatts) { if (array) _bt_array_set_low_or_high(rel, cur, array, ScanDirectionIsForward(dir)); continue; } /* * Search in scankey's array for the corresponding tuple attribute * value from caller's tuple */ tupdatum = index_getattr(tuple, cur->sk_attno, tupdesc, &tupnull); if (array) { bool cur_elem_trig = (sktrig_required && ikey == sktrig); /* * "Binary search" by checking if tupdatum/tupnull are within the * range of the skip array */ if (array->num_elems == -1) _bt_binsrch_skiparray_skey(cur_elem_trig, dir, tupdatum, tupnull, array, cur, &result); /* * Binary search for the closest match from the SAOP array */ else set_elem = _bt_binsrch_array_skey(&so->orderProcs[ikey], cur_elem_trig, dir, tupdatum, tupnull, array, cur, &result); } else { Assert(required); /* * This is a required non-array equality strategy scan key, which * we'll treat as a degenerate single element array. * * This scan key's imaginary "array" can't really advance, but it * can still roll over like any other array. (Actually, this is * no different to real single value arrays, which never advance * without rolling over -- they can never truly advance, either.) */ result = _bt_compare_array_skey(&so->orderProcs[ikey], tupdatum, tupnull, cur->sk_argument, cur); } /* * Consider "beyond end of array element" array advancement. * * When the tuple attribute value is > the closest matching array key * (or < in the backwards scan case), we need to ratchet this array * forward (backward) by one increment, so that caller's tuple ends up * being < final array value instead (or > final array value instead). * This process has to work for all of the arrays, not just this one: * it must "carry" to higher-order arrays when the set_elem that we * just found happens to be the final one for the scan's direction. * Incrementing (decrementing) set_elem itself isn't good enough. * * Our approach is to provisionally use set_elem as if it was an exact * match now, then set each later/less significant array to whatever * its final element is. Once outside the loop we'll then "increment * this array's set_elem" by calling _bt_advance_array_keys_increment. * That way the process rolls over to higher order arrays as needed. * * Under this scheme any required arrays only ever ratchet forwards * (or backwards), and always do so to the maximum possible extent * that we can know will be safe without seeing the scan's next tuple. * We don't need any special handling for required scan keys that lack * a real array to advance, nor for redundant scan keys that couldn't * be eliminated by _bt_preprocess_keys. It won't matter if some of * our "true" array scan keys (or even all of them) are non-required. */ if (sktrig_required && required && ((ScanDirectionIsForward(dir) && result > 0) || (ScanDirectionIsBackward(dir) && result < 0))) beyond_end_advance = true; Assert(all_required_satisfied && all_satisfied); if (result != 0) { /* * Track whether caller's tuple satisfies our new post-advancement * qual, for required scan keys, as well as for the entire set of * interesting scan keys (all required scan keys plus non-required * array scan keys are considered interesting.) */ all_satisfied = false; if (sktrig_required && required) all_required_satisfied = false; else { /* * There's no need to advance the arrays using the best * available match for a non-required array. Give up now. * (Though note that sktrig_required calls still have to do * all the usual post-advancement steps, including the recheck * call to _bt_check_compare.) */ break; } } /* Advance array keys, even when we don't have an exact match */ if (array) { if (array->num_elems == -1) { /* Skip array's new element is tupdatum (or MINVAL/MAXVAL) */ _bt_skiparray_set_element(rel, cur, array, result, tupdatum, tupnull); skip_array_advanced = true; } else if (array->cur_elem != set_elem) { /* SAOP array's new element is set_elem datum */ array->cur_elem = set_elem; cur->sk_argument = array->elem_values[set_elem]; } } } /* * Advance the array keys incrementally whenever "beyond end of array * element" array advancement happens, so that advancement will carry to * higher-order arrays (might exhaust all the scan's arrays instead, which * ends the top-level scan). */ if (beyond_end_advance && !_bt_advance_array_keys_increment(scan, dir, &skip_array_advanced)) goto end_toplevel_scan; Assert(_bt_verify_keys_with_arraykeys(scan)); /* * Maintain a page-level count of the number of times the scan's array * keys advanced in a way that affected at least one skip array */ if (sktrig_required && skip_array_advanced) pstate->nskipadvances++; /* * Does tuple now satisfy our new qual? Recheck with _bt_check_compare. * * Calls triggered by an unsatisfied required scan key, whose tuple now * satisfies all required scan keys, but not all nonrequired array keys, * will still require a recheck call to _bt_check_compare. They'll still * need its "second pass" handling of required inequality scan keys. * (Might have missed a still-unsatisfied required inequality scan key * that caller didn't detect as the sktrig scan key during its initial * _bt_check_compare call that used the old/original qual.) * * Calls triggered by an unsatisfied nonrequired array scan key never need * "second pass" handling of required inequalities (nor any other handling * of any required scan key). All that matters is whether caller's tuple * satisfies the new qual, so it's safe to just skip the _bt_check_compare * recheck when we've already determined that it can only return 'false'. * * Note: In practice most scan keys are marked required by preprocessing, * if necessary by generating a preceding skip array. We nevertheless * often handle array keys marked required as if they were nonrequired. * This behavior is requested by our _bt_check_compare caller, though only * when it is passed "forcenonrequired=true" by _bt_checkkeys. */ if ((sktrig_required && all_required_satisfied) || (!sktrig_required && all_satisfied)) { int nsktrig = sktrig + 1; bool continuescan; Assert(all_required_satisfied); /* Recheck _bt_check_compare on behalf of caller */ if (_bt_check_compare(scan, dir, tuple, tupnatts, tupdesc, false, !sktrig_required, &continuescan, &nsktrig) && !so->scanBehind) { /* This tuple satisfies the new qual */ Assert(all_satisfied && continuescan); if (pstate) pstate->continuescan = true; return true; } /* * Consider "second pass" handling of required inequalities. * * It's possible that our _bt_check_compare call indicated that the * scan should end due to some unsatisfied inequality that wasn't * initially recognized as such by us. Handle this by calling * ourselves recursively, this time indicating that the trigger is the * inequality that we missed first time around (and using a set of * required array/equality keys that are now exact matches for tuple). * * We make a strong, general guarantee that every _bt_checkkeys call * here will advance the array keys to the maximum possible extent * that we can know to be safe based on caller's tuple alone. If we * didn't perform this step, then that guarantee wouldn't quite hold. */ if (unlikely(!continuescan)) { bool satisfied PG_USED_FOR_ASSERTS_ONLY; Assert(sktrig_required); Assert(so->keyData[nsktrig].sk_strategy != BTEqualStrategyNumber); /* * The tuple must use "beyond end" advancement during the * recursive call, so we cannot possibly end up back here when * recursing. We'll consume a small, fixed amount of stack space. */ Assert(!beyond_end_advance); /* Advance the array keys a second time using same tuple */ satisfied = _bt_advance_array_keys(scan, pstate, tuple, tupnatts, tupdesc, nsktrig, true); /* This tuple doesn't satisfy the inequality */ Assert(!satisfied); return false; } /* * Some non-required scan key (from new qual) still not satisfied. * * All scan keys required in the current scan direction must still be * satisfied, though, so we can trust all_required_satisfied below. */ } /* * When we were called just to deal with "advancing" non-required arrays, * this is as far as we can go (cannot stop the scan for these callers) */ if (!sktrig_required) { /* Caller's tuple doesn't match any qual */ return false; } /* * Postcondition array state assertion (for still-unsatisfied tuples). * * By here we have established that the scan's required arrays (scan must * have at least one required array) advanced, without becoming exhausted. * * Caller's tuple is now < the newly advanced array keys (or > when this * is a backwards scan), except in the case where we only got this far due * to an unsatisfied non-required scan key. Verify that with an assert. * * Note: we don't just quit at this point when all required scan keys were * found to be satisfied because we need to consider edge-cases involving * scan keys required in the opposite direction only; those aren't tracked * by all_required_satisfied. */ Assert(_bt_tuple_before_array_skeys(scan, dir, tuple, tupdesc, tupnatts, false, 0, NULL) == !all_required_satisfied); /* * We generally permit primitive index scans to continue onto the next * sibling page when the page's finaltup satisfies all required scan keys * at the point where we're between pages. * * If caller's tuple is also the page's finaltup, and we see that required * scan keys still aren't satisfied, start a new primitive index scan. */ if (!all_required_satisfied && pstate->finaltup == tuple) goto new_prim_scan; /* * Proactively check finaltup (don't wait until finaltup is reached by the * scan) when it might well turn out to not be satisfied later on. * * Note: if so->scanBehind hasn't already been set for finaltup by us, * it'll be set during this call to _bt_tuple_before_array_skeys. Either * way, it'll be set correctly (for the whole page) after this point. */ if (!all_required_satisfied && pstate->finaltup && _bt_tuple_before_array_skeys(scan, dir, pstate->finaltup, tupdesc, BTreeTupleGetNAtts(pstate->finaltup, rel), false, 0, &so->scanBehind)) goto new_prim_scan; /* * When we encounter a truncated finaltup high key attribute, we're * optimistic about the chances of its corresponding required scan key * being satisfied when we go on to recheck it against tuples from this * page's right sibling leaf page. We consider truncated attributes to be * satisfied by required scan keys, which allows the primitive index scan * to continue to the next leaf page. We must set so->scanBehind to true * to remember that the last page's finaltup had "satisfied" required scan * keys for one or more truncated attribute values (scan keys required in * _either_ scan direction). * * There is a chance that _bt_readpage (which checks so->scanBehind) will * find that even the sibling leaf page's finaltup is < the new array * keys. When that happens, our optimistic policy will have incurred a * single extra leaf page access that could have been avoided. * * A pessimistic policy would give backward scans a gratuitous advantage * over forward scans. We'd punish forward scans for applying more * accurate information from the high key, rather than just using the * final non-pivot tuple as finaltup, in the style of backward scans. * Being pessimistic would also give some scans with non-required arrays a * perverse advantage over similar scans that use required arrays instead. * * This is similar to our scan-level heuristics, below. They also set * scanBehind to speculatively continue the primscan onto the next page. */ if (so->scanBehind) { /* Truncated high key -- _bt_scanbehind_checkkeys recheck scheduled */ } /* * Handle inequalities marked required in the opposite scan direction. * They can also signal that we should start a new primitive index scan. * * It's possible that the scan is now positioned where "matching" tuples * begin, and that caller's tuple satisfies all scan keys required in the * current scan direction. But if caller's tuple still doesn't satisfy * other scan keys that are required in the opposite scan direction only * (e.g., a required >= strategy scan key when scan direction is forward), * it's still possible that there are many leaf pages before the page that * _bt_first could skip straight to. Groveling through all those pages * will always give correct answers, but it can be very inefficient. We * must avoid needlessly scanning extra pages. * * Separately, it's possible that _bt_check_compare set continuescan=false * for a scan key that's required in the opposite direction only. This is * a special case, that happens only when _bt_check_compare sees that the * inequality encountered a NULL value. This signals the end of non-NULL * values in the current scan direction, which is reason enough to end the * (primitive) scan. If this happens at the start of a large group of * NULL values, then we shouldn't expect to be called again until after * the scan has already read indefinitely-many leaf pages full of tuples * with NULL suffix values. (_bt_first is expected to skip over the group * of NULLs by applying a similar "deduce NOT NULL" rule of its own, which * involves consing up an explicit SK_SEARCHNOTNULL key.) * * Apply a test against finaltup to detect and recover from the problem: * if even finaltup doesn't satisfy such an inequality, we just skip by * starting a new primitive index scan. When we skip, we know for sure * that all of the tuples on the current page following caller's tuple are * also before the _bt_first-wise start of tuples for our new qual. That * at least suggests many more skippable pages beyond the current page. * (when so->scanBehind and so->oppositeDirCheck are set, this'll happen * when we test the next page's finaltup/high key instead.) */ else if (has_required_opposite_direction_only && pstate->finaltup && unlikely(!_bt_oppodir_checkkeys(scan, dir, pstate->finaltup))) { /* * Make sure that any SAOP arrays that were not marked required by * preprocessing are reset to their first element for this direction */ _bt_rewind_nonrequired_arrays(scan, dir); goto new_prim_scan; } continue_scan: /* * Stick with the ongoing primitive index scan for now. * * It's possible that later tuples will also turn out to have values that * are still < the now-current array keys (or > the current array keys). * Our caller will handle this by performing what amounts to a linear * search of the page, implemented by calling _bt_check_compare and then * _bt_tuple_before_array_skeys for each tuple. * * This approach has various advantages over a binary search of the page. * Repeated binary searches of the page (one binary search for every array * advancement) won't outperform a continuous linear search. While there * are workloads that a naive linear search won't handle well, our caller * has a "look ahead" fallback mechanism to deal with that problem. */ pstate->continuescan = true; /* Override _bt_check_compare */ so->needPrimScan = false; /* _bt_readpage has more tuples to check */ if (so->scanBehind) { /* * Remember if recheck needs to call _bt_oppodir_checkkeys for next * page's finaltup (see above comments about "Handle inequalities * marked required in the opposite scan direction" for why). */ so->oppositeDirCheck = has_required_opposite_direction_only; _bt_rewind_nonrequired_arrays(scan, dir); /* * skip by setting "look ahead" mechanism's offnum for forwards scans * (backwards scans check scanBehind flag directly instead) */ if (ScanDirectionIsForward(dir)) pstate->skip = pstate->maxoff + 1; } /* Caller's tuple doesn't match the new qual */ return false; new_prim_scan: Assert(pstate->finaltup); /* not on rightmost/leftmost page */ /* * Looks like another primitive index scan is required. But consider * continuing the current primscan based on scan-level heuristics. * * Continue the ongoing primitive scan (and schedule a recheck for when * the scan arrives on the next sibling leaf page) when it has already * read at least one leaf page before the one we're reading now. This * makes primscan scheduling more efficient when scanning subsets of an * index with many distinct attribute values matching many array elements. * It encourages fewer, larger primitive scans where that makes sense. * This will in turn encourage _bt_readpage to apply the pstate.startikey * optimization more often. * * Also continue the ongoing primitive index scan when it is still on the * first page if there have been more than NSKIPADVANCES_THRESHOLD calls * here that each advanced at least one of the scan's skip arrays * (deliberately ignore advancements that only affected SAOP arrays here). * A page that cycles through this many skip array elements is quite * likely to neighbor similar pages, that we'll also need to read. * * Note: These heuristics aren't as aggressive as you might think. We're * conservative about allowing a primitive scan to step from the first * leaf page it reads to the page's sibling page (we only allow it on * first pages whose finaltup strongly suggests that it'll work out, as * well as first pages that have a large number of skip array advances). * Clearing this first page finaltup hurdle is a strong signal in itself. * * Note: The NSKIPADVANCES_THRESHOLD heuristic exists only to avoid * pathological cases. Specifically, cases where a skip scan should just * behave like a traditional full index scan, but ends up "skipping" again * and again, descending to the prior leaf page's direct sibling leaf page * each time. This misbehavior would otherwise be possible during scans * that never quite manage to "clear the first page finaltup hurdle". */ if (!pstate->firstpage || pstate->nskipadvances > NSKIPADVANCES_THRESHOLD) { /* Schedule a recheck once on the next (or previous) page */ so->scanBehind = true; /* Continue the current primitive scan after all */ goto continue_scan; } /* * End this primitive index scan, but schedule another. * * Note: We make a soft assumption that the current scan direction will * also be used within _bt_next, when it is asked to step off this page. * It is up to _bt_next to cancel this scheduled primitive index scan * whenever it steps to a page in the direction opposite currPos.dir. */ pstate->continuescan = false; /* Tell _bt_readpage we're done... */ so->needPrimScan = true; /* ...but call _bt_first again */ if (scan->parallel_scan) _bt_parallel_primscan_schedule(scan, so->currPos.currPage); /* Caller's tuple doesn't match the new qual */ return false; end_toplevel_scan: /* * End the current primitive index scan, but don't schedule another. * * This ends the entire top-level scan in the current scan direction. * * Note: The scan's arrays (including any non-required arrays) are now in * their final positions for the current scan direction. If the scan * direction happens to change, then the arrays will already be in their * first positions for what will then be the current scan direction. */ pstate->continuescan = false; /* Tell _bt_readpage we're done... */ so->needPrimScan = false; /* ...and don't call _bt_first again */ /* Caller's tuple doesn't match any qual */ return false; } #ifdef USE_ASSERT_CHECKING /* * Verify that the scan's qual state matches what we expect at the point that * _bt_start_prim_scan is about to start a just-scheduled new primitive scan. * * We enforce a rule against non-required array scan keys: they must start out * with whatever element is the first for the scan's current scan direction. * See _bt_rewind_nonrequired_arrays comments for an explanation. */ static bool _bt_verify_arrays_bt_first(IndexScanDesc scan, ScanDirection dir) { BTScanOpaque so = (BTScanOpaque) scan->opaque; int arrayidx = 0; for (int ikey = 0; ikey < so->numberOfKeys; ikey++) { ScanKey cur = so->keyData + ikey; BTArrayKeyInfo *array = NULL; int first_elem_dir; if (!(cur->sk_flags & SK_SEARCHARRAY) || cur->sk_strategy != BTEqualStrategyNumber) continue; array = &so->arrayKeys[arrayidx++]; if (((cur->sk_flags & SK_BT_REQFWD) && ScanDirectionIsForward(dir)) || ((cur->sk_flags & SK_BT_REQBKWD) && ScanDirectionIsBackward(dir))) continue; if (ScanDirectionIsForward(dir)) first_elem_dir = 0; else first_elem_dir = array->num_elems - 1; if (array->cur_elem != first_elem_dir) return false; } return _bt_verify_keys_with_arraykeys(scan); } /* * Verify that the scan's "so->keyData[]" scan keys are in agreement with * its array key state */ static bool _bt_verify_keys_with_arraykeys(IndexScanDesc scan) { BTScanOpaque so = (BTScanOpaque) scan->opaque; int last_sk_attno = InvalidAttrNumber, arrayidx = 0; if (!so->qual_ok) return false; for (int ikey = 0; ikey < so->numberOfKeys; ikey++) { ScanKey cur = so->keyData + ikey; BTArrayKeyInfo *array; if (cur->sk_strategy != BTEqualStrategyNumber || !(cur->sk_flags & SK_SEARCHARRAY)) continue; array = &so->arrayKeys[arrayidx++]; if (array->scan_key != ikey) return false; if (array->num_elems == 0 || array->num_elems < -1) return false; if (array->num_elems != -1 && cur->sk_argument != array->elem_values[array->cur_elem]) return false; if (last_sk_attno > cur->sk_attno) return false; last_sk_attno = cur->sk_attno; } if (arrayidx != so->numArrayKeys) return false; return true; } #endif /* * Test whether an indextuple satisfies all the scankey conditions. * * Return true if so, false if not. If the tuple fails to pass the qual, * we also determine whether there's any need to continue the scan beyond * this tuple, and set pstate.continuescan accordingly. See comments for * _bt_preprocess_keys() about how this is done. * * Forward scan callers can pass a high key tuple in the hopes of having * us set *continuescan to false, and avoiding an unnecessary visit to * the page to the right. * * Advances the scan's array keys when necessary for arrayKeys=true callers. * Scans without any array keys must always pass arrayKeys=false. * * Also stops and starts primitive index scans for arrayKeys=true callers. * Scans with array keys are required to set up page state that helps us with * this. The page's finaltup tuple (the page high key for a forward scan, or * the page's first non-pivot tuple for a backward scan) must be set in * pstate.finaltup ahead of the first call here for the page. Set this to * NULL for rightmost page (or the leftmost page for backwards scans). * * scan: index scan descriptor (containing a search-type scankey) * pstate: page level input and output parameters * arrayKeys: should we advance the scan's array keys if necessary? * tuple: index tuple to test * tupnatts: number of attributes in tupnatts (high key may be truncated) */ bool _bt_checkkeys(IndexScanDesc scan, BTReadPageState *pstate, bool arrayKeys, IndexTuple tuple, int tupnatts) { TupleDesc tupdesc = RelationGetDescr(scan->indexRelation); BTScanOpaque so = (BTScanOpaque) scan->opaque; ScanDirection dir = so->currPos.dir; int ikey = pstate->startikey; bool res; Assert(BTreeTupleGetNAtts(tuple, scan->indexRelation) == tupnatts); Assert(!so->needPrimScan && !so->scanBehind && !so->oppositeDirCheck); Assert(arrayKeys || so->numArrayKeys == 0); res = _bt_check_compare(scan, dir, tuple, tupnatts, tupdesc, arrayKeys, pstate->forcenonrequired, &pstate->continuescan, &ikey); /* * If _bt_check_compare relied on the pstate.startikey optimization, call * again (in assert-enabled builds) to verify it didn't affect our answer. * * Note: we can't do this when !pstate.forcenonrequired, since any arrays * before pstate.startikey won't have advanced on this page at all. */ Assert(!pstate->forcenonrequired || arrayKeys); #ifdef USE_ASSERT_CHECKING if (pstate->startikey > 0 && !pstate->forcenonrequired) { bool dres, dcontinuescan; int dikey = 0; /* Pass arrayKeys=false to avoid array side-effects */ dres = _bt_check_compare(scan, dir, tuple, tupnatts, tupdesc, false, pstate->forcenonrequired, &dcontinuescan, &dikey); Assert(res == dres); Assert(pstate->continuescan == dcontinuescan); /* * Should also get the same ikey result. We need a slightly weaker * assertion during arrayKeys calls, since they might be using an * array that couldn't be marked required during preprocessing. */ Assert(arrayKeys || ikey == dikey); Assert(ikey <= dikey); } #endif /* * Only one _bt_check_compare call is required in the common case where * there are no equality strategy array scan keys. Otherwise we can only * accept _bt_check_compare's answer unreservedly when it didn't set * pstate.continuescan=false. */ if (!arrayKeys || pstate->continuescan) return res; /* * _bt_check_compare call set continuescan=false in the presence of * equality type array keys. This could mean that the tuple is just past * the end of matches for the current array keys. * * It's also possible that the scan is still _before_ the _start_ of * tuples matching the current set of array keys. Check for that first. */ Assert(!pstate->forcenonrequired); if (_bt_tuple_before_array_skeys(scan, dir, tuple, tupdesc, tupnatts, true, ikey, NULL)) { /* Override _bt_check_compare, continue primitive scan */ pstate->continuescan = true; /* * We will end up here repeatedly given a group of tuples > the * previous array keys and < the now-current keys (for a backwards * scan it's just the same, though the operators swap positions). * * We must avoid allowing this linear search process to scan very many * tuples from well before the start of tuples matching the current * array keys (or from well before the point where we'll once again * have to advance the scan's array keys). * * We keep the overhead under control by speculatively "looking ahead" * to later still-unscanned items from this same leaf page. We'll * only attempt this once the number of tuples that the linear search * process has examined starts to get out of hand. */ pstate->rechecks++; if (pstate->rechecks >= LOOK_AHEAD_REQUIRED_RECHECKS) { /* See if we should skip ahead within the current leaf page */ _bt_checkkeys_look_ahead(scan, pstate, tupnatts, tupdesc); /* * Might have set pstate.skip to a later page offset. When that * happens then _bt_readpage caller will inexpensively skip ahead * to a later tuple from the same page (the one just after the * tuple we successfully "looked ahead" to). */ } /* This indextuple doesn't match the current qual, in any case */ return false; } /* * Caller's tuple is >= the current set of array keys and other equality * constraint scan keys (or <= if this is a backwards scan). It's now * clear that we _must_ advance any required array keys in lockstep with * the scan. */ return _bt_advance_array_keys(scan, pstate, tuple, tupnatts, tupdesc, ikey, true); } /* * Test whether caller's finaltup tuple is still before the start of matches * for the current array keys. * * Called at the start of reading a page during a scan with array keys, though * only when the so->scanBehind flag was set on the scan's prior page. * * Returns false if the tuple is still before the start of matches. When that * happens, caller should cut its losses and start a new primitive index scan. * Otherwise returns true. */ bool _bt_scanbehind_checkkeys(IndexScanDesc scan, ScanDirection dir, IndexTuple finaltup) { Relation rel = scan->indexRelation; TupleDesc tupdesc = RelationGetDescr(rel); BTScanOpaque so = (BTScanOpaque) scan->opaque; int nfinaltupatts = BTreeTupleGetNAtts(finaltup, rel); bool scanBehind; Assert(so->numArrayKeys); if (_bt_tuple_before_array_skeys(scan, dir, finaltup, tupdesc, nfinaltupatts, false, 0, &scanBehind)) return false; /* * If scanBehind was set, all of the untruncated attribute values from * finaltup that correspond to an array match the array's current element, * but there are other keys associated with truncated suffix attributes. * Array advancement must have incremented the scan's arrays on the * previous page, resulting in a set of array keys that happen to be an * exact match for the current page high key's untruncated prefix values. * * This page definitely doesn't contain tuples that the scan will need to * return. The next page may or may not contain relevant tuples. Handle * this by cutting our losses and starting a new primscan. */ if (scanBehind) return false; if (!so->oppositeDirCheck) return true; return _bt_oppodir_checkkeys(scan, dir, finaltup); } /* * Test whether an indextuple fails to satisfy an inequality required in the * opposite direction only. * * Caller's finaltup tuple is the page high key (for forwards scans), or the * first non-pivot tuple (for backwards scans). Called during scans with * required array keys and required opposite-direction inequalities. * * Returns false if an inequality scan key required in the opposite direction * only isn't satisfied (and any earlier required scan keys are satisfied). * Otherwise returns true. * * An unsatisfied inequality required in the opposite direction only might * well enable skipping over many leaf pages, provided another _bt_first call * takes place. This type of unsatisfied inequality won't usually cause * _bt_checkkeys to stop the scan to consider array advancement/starting a new * primitive index scan. */ static bool _bt_oppodir_checkkeys(IndexScanDesc scan, ScanDirection dir, IndexTuple finaltup) { Relation rel = scan->indexRelation; TupleDesc tupdesc = RelationGetDescr(rel); BTScanOpaque so = (BTScanOpaque) scan->opaque; int nfinaltupatts = BTreeTupleGetNAtts(finaltup, rel); bool continuescan; ScanDirection flipped = -dir; int ikey = 0; Assert(so->numArrayKeys); _bt_check_compare(scan, flipped, finaltup, nfinaltupatts, tupdesc, false, false, &continuescan, &ikey); if (!continuescan && so->keyData[ikey].sk_strategy != BTEqualStrategyNumber) return false; return true; } /* * Determines an offset to the first scan key (an so->keyData[]-wise offset) * that is _not_ guaranteed to be satisfied by every tuple from pstate.page, * which is set in pstate.startikey for _bt_checkkeys calls for the page. * This allows caller to save cycles on comparisons of a prefix of keys while * reading pstate.page. * * Also determines if later calls to _bt_checkkeys (for pstate.page) should be * forced to treat all required scan keys >= pstate.startikey as nonrequired * (that is, if they're to be treated as if any SK_BT_REQFWD/SK_BT_REQBKWD * markings that were set by preprocessing were not set at all, for the * duration of _bt_checkkeys calls prior to the call for pstate.finaltup). * This is indicated to caller by setting pstate.forcenonrequired. * * Call here at the start of reading a leaf page beyond the first one for the * primitive index scan. We consider all non-pivot tuples, so it doesn't make * sense to call here when only a subset of those tuples can ever be read. * This is also a good idea on performance grounds; not calling here when on * the first page (first for the current primitive scan) avoids wasting cycles * during selective point queries. They typically don't stand to gain as much * when we can set pstate.startikey, and are likely to notice the overhead of * calling here. (Also, allowing pstate.forcenonrequired to be set on a * primscan's first page would mislead _bt_advance_array_keys, which expects * pstate.nskipadvances to be representative of every first page's key space.) * * Caller must call _bt_start_array_keys and reset startikey/forcenonrequired * ahead of the finaltup _bt_checkkeys call when we set forcenonrequired=true. * This will give _bt_checkkeys the opportunity to call _bt_advance_array_keys * with sktrig_required=true, restoring the invariant that the scan's required * arrays always track the scan's progress through the index's key space. * Caller won't need to do this on the rightmost/leftmost page in the index * (where pstate.finaltup isn't ever set), since forcenonrequired will never * be set here in the first place. */ void _bt_set_startikey(IndexScanDesc scan, BTReadPageState *pstate) { BTScanOpaque so = (BTScanOpaque) scan->opaque; Relation rel = scan->indexRelation; TupleDesc tupdesc = RelationGetDescr(rel); ItemId iid; IndexTuple firsttup, lasttup; int startikey = 0, arrayidx = 0, firstchangingattnum; bool start_past_saop_eq = false; Assert(!so->scanBehind); Assert(pstate->minoff < pstate->maxoff); Assert(!pstate->firstpage); Assert(pstate->startikey == 0); Assert(!so->numArrayKeys || pstate->finaltup || P_RIGHTMOST(BTPageGetOpaque(pstate->page)) || P_LEFTMOST(BTPageGetOpaque(pstate->page))); if (so->numberOfKeys == 0) return; /* minoff is an offset to the lowest non-pivot tuple on the page */ iid = PageGetItemId(pstate->page, pstate->minoff); firsttup = (IndexTuple) PageGetItem(pstate->page, iid); /* maxoff is an offset to the highest non-pivot tuple on the page */ iid = PageGetItemId(pstate->page, pstate->maxoff); lasttup = (IndexTuple) PageGetItem(pstate->page, iid); /* Determine the first attribute whose values change on caller's page */ firstchangingattnum = _bt_keep_natts_fast(rel, firsttup, lasttup); for (; startikey < so->numberOfKeys; startikey++) { ScanKey key = so->keyData + startikey; BTArrayKeyInfo *array; Datum firstdatum, lastdatum; bool firstnull, lastnull; int32 result; /* * Determine if it's safe to set pstate.startikey to an offset to a * key that comes after this key, by examining this key */ if (!(key->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD))) { /* Scan key isn't marked required (corner case) */ Assert(!(key->sk_flags & SK_ROW_HEADER)); break; /* unsafe */ } if (key->sk_flags & SK_ROW_HEADER) { /* * RowCompare inequality. * * Only the first subkey from a RowCompare can ever be marked * required (that happens when the row header is marked required). * There is no simple, general way for us to transitively deduce * whether or not every tuple on the page satisfies a RowCompare * key based only on firsttup and lasttup -- so we just give up. */ if (!start_past_saop_eq && !so->skipScan) break; /* unsafe to go further */ /* * We have to be even more careful with RowCompares that come * after an array: we assume it's unsafe to even bypass the array. * Calling _bt_start_array_keys to recover the scan's arrays * following use of forcenonrequired mode isn't compatible with * _bt_check_rowcompare's continuescan=false behavior with NULL * row compare members. _bt_advance_array_keys must not make a * decision on the basis of a key not being satisfied in the * opposite-to-scan direction until the scan reaches a leaf page * where the same key begins to be satisfied in scan direction. * The _bt_first !used_all_subkeys behavior makes this limitation * hard to work around some other way. */ return; /* completely unsafe to set pstate.startikey */ } if (key->sk_strategy != BTEqualStrategyNumber) { /* * Scalar inequality key. * * It's definitely safe for _bt_checkkeys to avoid assessing this * inequality when the page's first and last non-pivot tuples both * satisfy the inequality (since the same must also be true of all * the tuples in between these two). * * Unlike the "=" case, it doesn't matter if this attribute has * more than one distinct value (though it _is_ necessary for any * and all _prior_ attributes to contain no more than one distinct * value amongst all of the tuples from pstate.page). */ if (key->sk_attno > firstchangingattnum) /* >, not >= */ break; /* unsafe, preceding attr has multiple * distinct values */ firstdatum = index_getattr(firsttup, key->sk_attno, tupdesc, &firstnull); lastdatum = index_getattr(lasttup, key->sk_attno, tupdesc, &lastnull); if (key->sk_flags & SK_ISNULL) { /* IS NOT NULL key */ Assert(key->sk_flags & SK_SEARCHNOTNULL); if (firstnull || lastnull) break; /* unsafe */ /* Safe, IS NOT NULL key satisfied by every tuple */ continue; } /* Test firsttup */ if (firstnull || !DatumGetBool(FunctionCall2Coll(&key->sk_func, key->sk_collation, firstdatum, key->sk_argument))) break; /* unsafe */ /* Test lasttup */ if (lastnull || !DatumGetBool(FunctionCall2Coll(&key->sk_func, key->sk_collation, lastdatum, key->sk_argument))) break; /* unsafe */ /* Safe, scalar inequality satisfied by every tuple */ continue; } /* Some = key (could be a scalar = key, could be an array = key) */ Assert(key->sk_strategy == BTEqualStrategyNumber); if (!(key->sk_flags & SK_SEARCHARRAY)) { /* * Scalar = key (possibly an IS NULL key). * * It is unsafe to set pstate.startikey to an ikey beyond this * key, unless the = key is satisfied by every possible tuple on * the page (possible only when attribute has just one distinct * value among all tuples on the page). */ if (key->sk_attno >= firstchangingattnum) break; /* unsafe, multiple distinct attr values */ firstdatum = index_getattr(firsttup, key->sk_attno, tupdesc, &firstnull); if (key->sk_flags & SK_ISNULL) { /* IS NULL key */ Assert(key->sk_flags & SK_SEARCHNULL); if (!firstnull) break; /* unsafe */ /* Safe, IS NULL key satisfied by every tuple */ continue; } if (firstnull || !DatumGetBool(FunctionCall2Coll(&key->sk_func, key->sk_collation, firstdatum, key->sk_argument))) break; /* unsafe */ /* Safe, scalar = key satisfied by every tuple */ continue; } /* = array key (could be a SAOP array, could be a skip array) */ array = &so->arrayKeys[arrayidx++]; Assert(array->scan_key == startikey); if (array->num_elems != -1) { /* * SAOP array = key. * * Handle this like we handle scalar = keys (though binary search * for a matching element, to avoid relying on key's sk_argument). */ if (key->sk_attno >= firstchangingattnum) break; /* unsafe, multiple distinct attr values */ firstdatum = index_getattr(firsttup, key->sk_attno, tupdesc, &firstnull); _bt_binsrch_array_skey(&so->orderProcs[startikey], false, NoMovementScanDirection, firstdatum, firstnull, array, key, &result); if (result != 0) break; /* unsafe */ /* Safe, SAOP = key satisfied by every tuple */ start_past_saop_eq = true; continue; } /* * Skip array = key */ Assert(key->sk_flags & SK_BT_SKIP); if (array->null_elem) { /* * Non-range skip array = key. * * Safe, non-range skip array "satisfied" by every tuple on page * (safe even when "key->sk_attno > firstchangingattnum"). */ continue; } /* * Range skip array = key. * * Handle this like we handle scalar inequality keys (but avoid using * key's sk_argument directly, as in the SAOP array case). */ if (key->sk_attno > firstchangingattnum) /* >, not >= */ break; /* unsafe, preceding attr has multiple * distinct values */ firstdatum = index_getattr(firsttup, key->sk_attno, tupdesc, &firstnull); lastdatum = index_getattr(lasttup, key->sk_attno, tupdesc, &lastnull); /* Test firsttup */ _bt_binsrch_skiparray_skey(false, ForwardScanDirection, firstdatum, firstnull, array, key, &result); if (result != 0) break; /* unsafe */ /* Test lasttup */ _bt_binsrch_skiparray_skey(false, ForwardScanDirection, lastdatum, lastnull, array, key, &result); if (result != 0) break; /* unsafe */ /* Safe, range skip array satisfied by every tuple on page */ } /* * Use of forcenonrequired is typically undesirable, since it'll force * _bt_readpage caller to read every tuple on the page -- even though, in * general, it might well be possible to end the scan on an earlier tuple. * However, caller must use forcenonrequired when start_past_saop_eq=true, * since the usual required array behavior might fail to roll over to the * SAOP array. * * We always prefer forcenonrequired=true during scans with skip arrays * (except on the first page of each primitive index scan), though -- even * when "startikey == 0". That way, _bt_advance_array_keys's low-order * key precheck optimization can always be used (unless on the first page * of the scan). It seems slightly preferable to check more tuples when * that allows us to do significantly less skip array maintenance. */ pstate->forcenonrequired = (start_past_saop_eq || so->skipScan); pstate->startikey = startikey; /* * _bt_readpage caller is required to call _bt_checkkeys against page's * finaltup with forcenonrequired=false whenever we initially set * forcenonrequired=true. That way the scan's arrays will reliably track * its progress through the index's key space. * * We don't expect this when _bt_readpage caller has no finaltup due to * its page being the rightmost (or the leftmost, during backwards scans). * When we see that _bt_readpage has no finaltup, back out of everything. */ Assert(!pstate->forcenonrequired || so->numArrayKeys); if (pstate->forcenonrequired && !pstate->finaltup) { pstate->forcenonrequired = false; pstate->startikey = 0; } } /* * Test whether an indextuple satisfies current scan condition. * * Return true if so, false if not. If not, also sets *continuescan to false * when it's also not possible for any later tuples to pass the current qual * (with the scan's current set of array keys, in the current scan direction), * in addition to setting *ikey to the so->keyData[] subscript/offset for the * unsatisfied scan key (needed when caller must consider advancing the scan's * array keys). * * This is a subroutine for _bt_checkkeys. We provisionally assume that * reaching the end of the current set of required keys (in particular the * current required array keys) ends the ongoing (primitive) index scan. * Callers without array keys should just end the scan right away when they * find that continuescan has been set to false here by us. Things are more * complicated for callers with array keys. * * Callers with array keys must first consider advancing the arrays when * continuescan has been set to false here by us. They must then consider if * it really does make sense to end the current (primitive) index scan, in * light of everything that is known at that point. (In general when we set * continuescan=false for these callers it must be treated as provisional.) * * We deal with advancing unsatisfied non-required arrays directly, though. * This is safe, since by definition non-required keys can't end the scan. * This is just how we determine if non-required arrays are just unsatisfied * by the current array key, or if they're truly unsatisfied (that is, if * they're unsatisfied by every possible array key). * * Pass advancenonrequired=false to avoid all array related side effects. * This allows _bt_advance_array_keys caller to avoid infinite recursion. * * Pass forcenonrequired=true to instruct us to treat all keys as nonrequired. * This is used to make it safe to temporarily stop properly maintaining the * scan's required arrays. _bt_checkkeys caller (_bt_readpage, actually) * determines a prefix of keys that must satisfy every possible corresponding * index attribute value from its page, which is passed to us via *ikey arg * (this is the first key that might be unsatisfied by tuples on the page). * Obviously, we won't maintain any array keys from before *ikey, so it's * quite possible for such arrays to "fall behind" the index's keyspace. * Caller will need to "catch up" by passing forcenonrequired=true (alongside * an *ikey=0) once the page's finaltup is reached. * * Note: it's safe to pass an *ikey > 0 with forcenonrequired=false, but only * when caller determines that it won't affect array maintenance. */ static bool _bt_check_compare(IndexScanDesc scan, ScanDirection dir, IndexTuple tuple, int tupnatts, TupleDesc tupdesc, bool advancenonrequired, bool forcenonrequired, bool *continuescan, int *ikey) { BTScanOpaque so = (BTScanOpaque) scan->opaque; *continuescan = true; /* default assumption */ for (; *ikey < so->numberOfKeys; (*ikey)++) { ScanKey key = so->keyData + *ikey; Datum datum; bool isNull; bool requiredSameDir = false, requiredOppositeDirOnly = false; /* * Check if the key is required in the current scan direction, in the * opposite scan direction _only_, or in neither direction (except * when we're forced to treat all scan keys as nonrequired) */ if (forcenonrequired) { /* treating scan's keys as non-required */ } else if (((key->sk_flags & SK_BT_REQFWD) && ScanDirectionIsForward(dir)) || ((key->sk_flags & SK_BT_REQBKWD) && ScanDirectionIsBackward(dir))) requiredSameDir = true; else if (((key->sk_flags & SK_BT_REQFWD) && ScanDirectionIsBackward(dir)) || ((key->sk_flags & SK_BT_REQBKWD) && ScanDirectionIsForward(dir))) requiredOppositeDirOnly = true; if (key->sk_attno > tupnatts) { /* * This attribute is truncated (must be high key). The value for * this attribute in the first non-pivot tuple on the page to the * right could be any possible value. Assume that truncated * attribute passes the qual. */ Assert(BTreeTupleIsPivot(tuple)); continue; } /* * A skip array scan key uses one of several sentinel values. We just * fall back on _bt_tuple_before_array_skeys when we see such a value. */ if (key->sk_flags & (SK_BT_MINVAL | SK_BT_MAXVAL | SK_BT_NEXT | SK_BT_PRIOR)) { Assert(key->sk_flags & SK_SEARCHARRAY); Assert(key->sk_flags & SK_BT_SKIP); Assert(requiredSameDir || forcenonrequired); /* * Cannot fall back on _bt_tuple_before_array_skeys when we're * treating the scan's keys as nonrequired, though. Just handle * this like any other non-required equality-type array key. */ if (forcenonrequired) return _bt_advance_array_keys(scan, NULL, tuple, tupnatts, tupdesc, *ikey, false); *continuescan = false; return false; } /* row-comparison keys need special processing */ if (key->sk_flags & SK_ROW_HEADER) { if (_bt_check_rowcompare(key, tuple, tupnatts, tupdesc, dir, forcenonrequired, continuescan)) continue; return false; } datum = index_getattr(tuple, key->sk_attno, tupdesc, &isNull); if (key->sk_flags & SK_ISNULL) { /* Handle IS NULL/NOT NULL tests */ if (key->sk_flags & SK_SEARCHNULL) { if (isNull) continue; /* tuple satisfies this qual */ } else { Assert(key->sk_flags & SK_SEARCHNOTNULL); Assert(!(key->sk_flags & SK_BT_SKIP)); if (!isNull) continue; /* tuple satisfies this qual */ } /* * Tuple fails this qual. If it's a required qual for the current * scan direction, then we can conclude no further tuples will * pass, either. */ if (requiredSameDir) *continuescan = false; else if (unlikely(key->sk_flags & SK_BT_SKIP)) { /* * If we're treating scan keys as nonrequired, and encounter a * skip array scan key whose current element is NULL, then it * must be a non-range skip array. It must be satisfied, so * there's no need to call _bt_advance_array_keys to check. */ Assert(forcenonrequired && *ikey > 0); continue; } /* * This indextuple doesn't match the qual. */ return false; } if (isNull) { /* * Scalar scan key isn't satisfied by NULL tuple value. * * If we're treating scan keys as nonrequired, and key is for a * skip array, then we must attempt to advance the array to NULL * (if we're successful then the tuple might match the qual). */ if (unlikely(forcenonrequired && key->sk_flags & SK_BT_SKIP)) return _bt_advance_array_keys(scan, NULL, tuple, tupnatts, tupdesc, *ikey, false); if (key->sk_flags & SK_BT_NULLS_FIRST) { /* * Since NULLs are sorted before non-NULLs, we know we have * reached the lower limit of the range of values for this * index attr. On a backward scan, we can stop if this qual * is one of the "must match" subset. We can stop regardless * of whether the qual is > or <, so long as it's required, * because it's not possible for any future tuples to pass. On * a forward scan, however, we must keep going, because we may * have initially positioned to the start of the index. * (_bt_advance_array_keys also relies on this behavior during * forward scans.) */ if ((requiredSameDir || requiredOppositeDirOnly) && ScanDirectionIsBackward(dir)) *continuescan = false; } else { /* * Since NULLs are sorted after non-NULLs, we know we have * reached the upper limit of the range of values for this * index attr. On a forward scan, we can stop if this qual is * one of the "must match" subset. We can stop regardless of * whether the qual is > or <, so long as it's required, * because it's not possible for any future tuples to pass. On * a backward scan, however, we must keep going, because we * may have initially positioned to the end of the index. * (_bt_advance_array_keys also relies on this behavior during * backward scans.) */ if ((requiredSameDir || requiredOppositeDirOnly) && ScanDirectionIsForward(dir)) *continuescan = false; } /* * This indextuple doesn't match the qual. */ return false; } if (!DatumGetBool(FunctionCall2Coll(&key->sk_func, key->sk_collation, datum, key->sk_argument))) { /* * Tuple fails this qual. If it's a required qual for the current * scan direction, then we can conclude no further tuples will * pass, either. * * Note: because we stop the scan as soon as any required equality * qual fails, it is critical that equality quals be used for the * initial positioning in _bt_first() when they are available. See * comments in _bt_first(). */ if (requiredSameDir) *continuescan = false; /* * If this is a non-required equality-type array key, the tuple * needs to be checked against every possible array key. Handle * this by "advancing" the scan key's array to a matching value * (if we're successful then the tuple might match the qual). */ else if (advancenonrequired && key->sk_strategy == BTEqualStrategyNumber && (key->sk_flags & SK_SEARCHARRAY)) return _bt_advance_array_keys(scan, NULL, tuple, tupnatts, tupdesc, *ikey, false); /* * This indextuple doesn't match the qual. */ return false; } } /* If we get here, the tuple passes all index quals. */ return true; } /* * Test whether an indextuple satisfies a row-comparison scan condition. * * Return true if so, false if not. If not, also clear *continuescan if * it's not possible for any future tuples in the current scan direction * to pass the qual. * * This is a subroutine for _bt_checkkeys/_bt_check_compare. */ static bool _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, TupleDesc tupdesc, ScanDirection dir, bool forcenonrequired, bool *continuescan) { ScanKey subkey = (ScanKey) DatumGetPointer(skey->sk_argument); int32 cmpresult = 0; bool result; /* First subkey should be same as the header says */ Assert(subkey->sk_attno == skey->sk_attno); /* Loop over columns of the row condition */ for (;;) { Datum datum; bool isNull; Assert(subkey->sk_flags & SK_ROW_MEMBER); if (subkey->sk_attno > tupnatts) { /* * This attribute is truncated (must be high key). The value for * this attribute in the first non-pivot tuple on the page to the * right could be any possible value. Assume that truncated * attribute passes the qual. */ Assert(BTreeTupleIsPivot(tuple)); cmpresult = 0; if (subkey->sk_flags & SK_ROW_END) break; subkey++; continue; } datum = index_getattr(tuple, subkey->sk_attno, tupdesc, &isNull); if (isNull) { if (forcenonrequired) { /* treating scan's keys as non-required */ } else if (subkey->sk_flags & SK_BT_NULLS_FIRST) { /* * Since NULLs are sorted before non-NULLs, we know we have * reached the lower limit of the range of values for this * index attr. On a backward scan, we can stop if this qual * is one of the "must match" subset. We can stop regardless * of whether the qual is > or <, so long as it's required, * because it's not possible for any future tuples to pass. On * a forward scan, however, we must keep going, because we may * have initially positioned to the start of the index. * (_bt_advance_array_keys also relies on this behavior during * forward scans.) */ if ((subkey->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)) && ScanDirectionIsBackward(dir)) *continuescan = false; } else { /* * Since NULLs are sorted after non-NULLs, we know we have * reached the upper limit of the range of values for this * index attr. On a forward scan, we can stop if this qual is * one of the "must match" subset. We can stop regardless of * whether the qual is > or <, so long as it's required, * because it's not possible for any future tuples to pass. On * a backward scan, however, we must keep going, because we * may have initially positioned to the end of the index. * (_bt_advance_array_keys also relies on this behavior during * backward scans.) */ if ((subkey->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)) && ScanDirectionIsForward(dir)) *continuescan = false; } /* * In any case, this indextuple doesn't match the qual. */ return false; } if (subkey->sk_flags & SK_ISNULL) { /* * Unlike the simple-scankey case, this isn't a disallowed case * (except when it's the first row element that has the NULL arg). * But it can never match. If all the earlier row comparison * columns are required for the scan direction, we can stop the * scan, because there can't be another tuple that will succeed. */ Assert(subkey != (ScanKey) DatumGetPointer(skey->sk_argument)); subkey--; if (forcenonrequired) { /* treating scan's keys as non-required */ } else if ((subkey->sk_flags & SK_BT_REQFWD) && ScanDirectionIsForward(dir)) *continuescan = false; else if ((subkey->sk_flags & SK_BT_REQBKWD) && ScanDirectionIsBackward(dir)) *continuescan = false; return false; } /* Perform the test --- three-way comparison not bool operator */ cmpresult = DatumGetInt32(FunctionCall2Coll(&subkey->sk_func, subkey->sk_collation, datum, subkey->sk_argument)); if (subkey->sk_flags & SK_BT_DESC) INVERT_COMPARE_RESULT(cmpresult); /* Done comparing if unequal, else advance to next column */ if (cmpresult != 0) break; if (subkey->sk_flags & SK_ROW_END) break; subkey++; } /* * At this point cmpresult indicates the overall result of the row * comparison, and subkey points to the deciding column (or the last * column if the result is "="). */ switch (subkey->sk_strategy) { /* EQ and NE cases aren't allowed here */ case BTLessStrategyNumber: result = (cmpresult < 0); break; case BTLessEqualStrategyNumber: result = (cmpresult <= 0); break; case BTGreaterEqualStrategyNumber: result = (cmpresult >= 0); break; case BTGreaterStrategyNumber: result = (cmpresult > 0); break; default: elog(ERROR, "unexpected strategy number %d", subkey->sk_strategy); result = 0; /* keep compiler quiet */ break; } if (!result && !forcenonrequired) { /* * Tuple fails this qual. If it's a required qual for the current * scan direction, then we can conclude no further tuples will pass, * either. Note we have to look at the deciding column, not * necessarily the first or last column of the row condition. */ if ((subkey->sk_flags & SK_BT_REQFWD) && ScanDirectionIsForward(dir)) *continuescan = false; else if ((subkey->sk_flags & SK_BT_REQBKWD) && ScanDirectionIsBackward(dir)) *continuescan = false; } return result; } /* * Determine if a scan with array keys should skip over uninteresting tuples. * * This is a subroutine for _bt_checkkeys. Called when _bt_readpage's linear * search process (started after it finishes reading an initial group of * matching tuples, used to locate the start of the next group of tuples * matching the next set of required array keys) has already scanned an * excessive number of tuples whose key space is "between arrays". * * When we perform look ahead successfully, we'll sets pstate.skip, which * instructs _bt_readpage to skip ahead to that tuple next (could be past the * end of the scan's leaf page). Pages where the optimization is effective * will generally still need to skip several times. Each call here performs * only a single "look ahead" comparison of a later tuple, whose distance from * the current tuple's offset number is determined by applying heuristics. */ static void _bt_checkkeys_look_ahead(IndexScanDesc scan, BTReadPageState *pstate, int tupnatts, TupleDesc tupdesc) { BTScanOpaque so = (BTScanOpaque) scan->opaque; ScanDirection dir = so->currPos.dir; OffsetNumber aheadoffnum; IndexTuple ahead; Assert(!pstate->forcenonrequired); /* Avoid looking ahead when comparing the page high key */ if (pstate->offnum < pstate->minoff) return; /* * Don't look ahead when there aren't enough tuples remaining on the page * (in the current scan direction) for it to be worth our while */ if (ScanDirectionIsForward(dir) && pstate->offnum >= pstate->maxoff - LOOK_AHEAD_DEFAULT_DISTANCE) return; else if (ScanDirectionIsBackward(dir) && pstate->offnum <= pstate->minoff + LOOK_AHEAD_DEFAULT_DISTANCE) return; /* * The look ahead distance starts small, and ramps up as each call here * allows _bt_readpage to skip over more tuples */ if (!pstate->targetdistance) pstate->targetdistance = LOOK_AHEAD_DEFAULT_DISTANCE; else if (pstate->targetdistance < MaxIndexTuplesPerPage / 2) pstate->targetdistance *= 2; /* Don't read past the end (or before the start) of the page, though */ if (ScanDirectionIsForward(dir)) aheadoffnum = Min((int) pstate->maxoff, (int) pstate->offnum + pstate->targetdistance); else aheadoffnum = Max((int) pstate->minoff, (int) pstate->offnum - pstate->targetdistance); ahead = (IndexTuple) PageGetItem(pstate->page, PageGetItemId(pstate->page, aheadoffnum)); if (_bt_tuple_before_array_skeys(scan, dir, ahead, tupdesc, tupnatts, false, 0, NULL)) { /* * Success -- instruct _bt_readpage to skip ahead to very next tuple * after the one we determined was still before the current array keys */ if (ScanDirectionIsForward(dir)) pstate->skip = aheadoffnum + 1; else pstate->skip = aheadoffnum - 1; } else { /* * Failure -- "ahead" tuple is too far ahead (we were too aggressive). * * Reset the number of rechecks, and aggressively reduce the target * distance (we're much more aggressive here than we were when the * distance was initially ramped up). */ pstate->rechecks = 0; pstate->targetdistance = Max(pstate->targetdistance / 8, 1); } } /* * _bt_killitems - set LP_DEAD state for items an indexscan caller has * told us were killed * * scan->opaque, referenced locally through so, contains information about the * current page and killed tuples thereon (generally, this should only be * called if so->numKilled > 0). * * Caller should not have a lock on the so->currPos page, but must hold a * buffer pin when !so->dropPin. When we return, it still won't be locked. * It'll continue to hold whatever pins were held before calling here. * * We match items by heap TID before assuming they are the right ones to set * LP_DEAD. If the scan is one that holds a buffer pin on the target page * continuously from initially reading the items until applying this function * (if it is a !so->dropPin scan), VACUUM cannot have deleted any items on the * page, so the page's TIDs can't have been recycled by now. There's no risk * that we'll confuse a new index tuple that happens to use a recycled TID * with a now-removed tuple with the same TID (that used to be on this same * page). We can't rely on that during scans that drop buffer pins eagerly * (so->dropPin scans), though, so we must condition setting LP_DEAD bits on * the page LSN having not changed since back when _bt_readpage saw the page. * We totally give up on setting LP_DEAD bits when the page LSN changed. * * We give up much less often during !so->dropPin scans, but it still happens. * We cope with cases where items have moved right due to insertions. If an * item has moved off the current page due to a split, we'll fail to find it * and just give up on it. */ void _bt_killitems(IndexScanDesc scan) { Relation rel = scan->indexRelation; BTScanOpaque so = (BTScanOpaque) scan->opaque; Page page; BTPageOpaque opaque; OffsetNumber minoff; OffsetNumber maxoff; int numKilled = so->numKilled; bool killedsomething = false; Buffer buf; Assert(numKilled > 0); Assert(BTScanPosIsValid(so->currPos)); Assert(scan->heapRelation != NULL); /* can't be a bitmap index scan */ /* Always invalidate so->killedItems[] before leaving so->currPos */ so->numKilled = 0; if (!so->dropPin) { /* * We have held the pin on this page since we read the index tuples, * so all we need to do is lock it. The pin will have prevented * concurrent VACUUMs from recycling any of the TIDs on the page. */ Assert(BTScanPosIsPinned(so->currPos)); buf = so->currPos.buf; _bt_lockbuf(rel, buf, BT_READ); } else { XLogRecPtr latestlsn; Assert(!BTScanPosIsPinned(so->currPos)); Assert(RelationNeedsWAL(rel)); buf = _bt_getbuf(rel, so->currPos.currPage, BT_READ); latestlsn = BufferGetLSNAtomic(buf); Assert(!XLogRecPtrIsInvalid(so->currPos.lsn)); Assert(so->currPos.lsn <= latestlsn); if (so->currPos.lsn != latestlsn) { /* Modified, give up on hinting */ _bt_relbuf(rel, buf); return; } /* Unmodified, hinting is safe */ } page = BufferGetPage(buf); opaque = BTPageGetOpaque(page); minoff = P_FIRSTDATAKEY(opaque); maxoff = PageGetMaxOffsetNumber(page); for (int i = 0; i < numKilled; i++) { int itemIndex = so->killedItems[i]; BTScanPosItem *kitem = &so->currPos.items[itemIndex]; OffsetNumber offnum = kitem->indexOffset; Assert(itemIndex >= so->currPos.firstItem && itemIndex <= so->currPos.lastItem); if (offnum < minoff) continue; /* pure paranoia */ while (offnum <= maxoff) { ItemId iid = PageGetItemId(page, offnum); IndexTuple ituple = (IndexTuple) PageGetItem(page, iid); bool killtuple = false; if (BTreeTupleIsPosting(ituple)) { int pi = i + 1; int nposting = BTreeTupleGetNPosting(ituple); int j; /* * We rely on the convention that heap TIDs in the scanpos * items array are stored in ascending heap TID order for a * group of TIDs that originally came from a posting list * tuple. This convention even applies during backwards * scans, where returning the TIDs in descending order might * seem more natural. This is about effectiveness, not * correctness. * * Note that the page may have been modified in almost any way * since we first read it (in the !so->dropPin case), so it's * possible that this posting list tuple wasn't a posting list * tuple when we first encountered its heap TIDs. */ for (j = 0; j < nposting; j++) { ItemPointer item = BTreeTupleGetPostingN(ituple, j); if (!ItemPointerEquals(item, &kitem->heapTid)) break; /* out of posting list loop */ /* * kitem must have matching offnum when heap TIDs match, * though only in the common case where the page can't * have been concurrently modified */ Assert(kitem->indexOffset == offnum || !so->dropPin); /* * Read-ahead to later kitems here. * * We rely on the assumption that not advancing kitem here * will prevent us from considering the posting list tuple * fully dead by not matching its next heap TID in next * loop iteration. * * If, on the other hand, this is the final heap TID in * the posting list tuple, then tuple gets killed * regardless (i.e. we handle the case where the last * kitem is also the last heap TID in the last index tuple * correctly -- posting tuple still gets killed). */ if (pi < numKilled) kitem = &so->currPos.items[so->killedItems[pi++]]; } /* * Don't bother advancing the outermost loop's int iterator to * avoid processing killed items that relate to the same * offnum/posting list tuple. This micro-optimization hardly * seems worth it. (Further iterations of the outermost loop * will fail to match on this same posting list's first heap * TID instead, so we'll advance to the next offnum/index * tuple pretty quickly.) */ if (j == nposting) killtuple = true; } else if (ItemPointerEquals(&ituple->t_tid, &kitem->heapTid)) killtuple = true; /* * Mark index item as dead, if it isn't already. Since this * happens while holding a buffer lock possibly in shared mode, * it's possible that multiple processes attempt to do this * simultaneously, leading to multiple full-page images being sent * to WAL (if wal_log_hints or data checksums are enabled), which * is undesirable. */ if (killtuple && !ItemIdIsDead(iid)) { /* found the item/all posting list items */ ItemIdMarkDead(iid); killedsomething = true; break; /* out of inner search loop */ } offnum = OffsetNumberNext(offnum); } } /* * Since this can be redone later if needed, mark as dirty hint. * * Whenever we mark anything LP_DEAD, we also set the page's * BTP_HAS_GARBAGE flag, which is likewise just a hint. (Note that we * only rely on the page-level flag in !heapkeyspace indexes.) */ if (killedsomething) { opaque->btpo_flags |= BTP_HAS_GARBAGE; MarkBufferDirtyHint(buf, true); } if (!so->dropPin) _bt_unlockbuf(rel, buf); else _bt_relbuf(rel, buf); } /* * The following routines manage a shared-memory area in which we track * assignment of "vacuum cycle IDs" to currently-active btree vacuuming * operations. There is a single counter which increments each time we * start a vacuum to assign it a cycle ID. Since multiple vacuums could * be active concurrently, we have to track the cycle ID for each active * vacuum; this requires at most MaxBackends entries (usually far fewer). * We assume at most one vacuum can be active for a given index. * * Access to the shared memory area is controlled by BtreeVacuumLock. * In principle we could use a separate lmgr locktag for each index, * but a single LWLock is much cheaper, and given the short time that * the lock is ever held, the concurrency hit should be minimal. */ typedef struct BTOneVacInfo { LockRelId relid; /* global identifier of an index */ BTCycleId cycleid; /* cycle ID for its active VACUUM */ } BTOneVacInfo; typedef struct BTVacInfo { BTCycleId cycle_ctr; /* cycle ID most recently assigned */ int num_vacuums; /* number of currently active VACUUMs */ int max_vacuums; /* allocated length of vacuums[] array */ BTOneVacInfo vacuums[FLEXIBLE_ARRAY_MEMBER]; } BTVacInfo; static BTVacInfo *btvacinfo; /* * _bt_vacuum_cycleid --- get the active vacuum cycle ID for an index, * or zero if there is no active VACUUM * * Note: for correct interlocking, the caller must already hold pin and * exclusive lock on each buffer it will store the cycle ID into. This * ensures that even if a VACUUM starts immediately afterwards, it cannot * process those pages until the page split is complete. */ BTCycleId _bt_vacuum_cycleid(Relation rel) { BTCycleId result = 0; int i; /* Share lock is enough since this is a read-only operation */ LWLockAcquire(BtreeVacuumLock, LW_SHARED); for (i = 0; i < btvacinfo->num_vacuums; i++) { BTOneVacInfo *vac = &btvacinfo->vacuums[i]; if (vac->relid.relId == rel->rd_lockInfo.lockRelId.relId && vac->relid.dbId == rel->rd_lockInfo.lockRelId.dbId) { result = vac->cycleid; break; } } LWLockRelease(BtreeVacuumLock); return result; } /* * _bt_start_vacuum --- assign a cycle ID to a just-starting VACUUM operation * * Note: the caller must guarantee that it will eventually call * _bt_end_vacuum, else we'll permanently leak an array slot. To ensure * that this happens even in elog(FATAL) scenarios, the appropriate coding * is not just a PG_TRY, but * PG_ENSURE_ERROR_CLEANUP(_bt_end_vacuum_callback, PointerGetDatum(rel)) */ BTCycleId _bt_start_vacuum(Relation rel) { BTCycleId result; int i; BTOneVacInfo *vac; LWLockAcquire(BtreeVacuumLock, LW_EXCLUSIVE); /* * Assign the next cycle ID, being careful to avoid zero as well as the * reserved high values. */ result = ++(btvacinfo->cycle_ctr); if (result == 0 || result > MAX_BT_CYCLE_ID) result = btvacinfo->cycle_ctr = 1; /* Let's just make sure there's no entry already for this index */ for (i = 0; i < btvacinfo->num_vacuums; i++) { vac = &btvacinfo->vacuums[i]; if (vac->relid.relId == rel->rd_lockInfo.lockRelId.relId && vac->relid.dbId == rel->rd_lockInfo.lockRelId.dbId) { /* * Unlike most places in the backend, we have to explicitly * release our LWLock before throwing an error. This is because * we expect _bt_end_vacuum() to be called before transaction * abort cleanup can run to release LWLocks. */ LWLockRelease(BtreeVacuumLock); elog(ERROR, "multiple active vacuums for index \"%s\"", RelationGetRelationName(rel)); } } /* OK, add an entry */ if (btvacinfo->num_vacuums >= btvacinfo->max_vacuums) { LWLockRelease(BtreeVacuumLock); elog(ERROR, "out of btvacinfo slots"); } vac = &btvacinfo->vacuums[btvacinfo->num_vacuums]; vac->relid = rel->rd_lockInfo.lockRelId; vac->cycleid = result; btvacinfo->num_vacuums++; LWLockRelease(BtreeVacuumLock); return result; } /* * _bt_end_vacuum --- mark a btree VACUUM operation as done * * Note: this is deliberately coded not to complain if no entry is found; * this allows the caller to put PG_TRY around the start_vacuum operation. */ void _bt_end_vacuum(Relation rel) { int i; LWLockAcquire(BtreeVacuumLock, LW_EXCLUSIVE); /* Find the array entry */ for (i = 0; i < btvacinfo->num_vacuums; i++) { BTOneVacInfo *vac = &btvacinfo->vacuums[i]; if (vac->relid.relId == rel->rd_lockInfo.lockRelId.relId && vac->relid.dbId == rel->rd_lockInfo.lockRelId.dbId) { /* Remove it by shifting down the last entry */ *vac = btvacinfo->vacuums[btvacinfo->num_vacuums - 1]; btvacinfo->num_vacuums--; break; } } LWLockRelease(BtreeVacuumLock); } /* * _bt_end_vacuum wrapped as an on_shmem_exit callback function */ void _bt_end_vacuum_callback(int code, Datum arg) { _bt_end_vacuum((Relation) DatumGetPointer(arg)); } /* * BTreeShmemSize --- report amount of shared memory space needed */ Size BTreeShmemSize(void) { Size size; size = offsetof(BTVacInfo, vacuums); size = add_size(size, mul_size(MaxBackends, sizeof(BTOneVacInfo))); return size; } /* * BTreeShmemInit --- initialize this module's shared memory */ void BTreeShmemInit(void) { bool found; btvacinfo = (BTVacInfo *) ShmemInitStruct("BTree Vacuum State", BTreeShmemSize(), &found); if (!IsUnderPostmaster) { /* Initialize shared memory area */ Assert(!found); /* * It doesn't really matter what the cycle counter starts at, but * having it always start the same doesn't seem good. Seed with * low-order bits of time() instead. */ btvacinfo->cycle_ctr = (BTCycleId) time(NULL); btvacinfo->num_vacuums = 0; btvacinfo->max_vacuums = MaxBackends; } else Assert(found); } bytea * btoptions(Datum reloptions, bool validate) { static const relopt_parse_elt tab[] = { {"fillfactor", RELOPT_TYPE_INT, offsetof(BTOptions, fillfactor)}, {"vacuum_cleanup_index_scale_factor", RELOPT_TYPE_REAL, offsetof(BTOptions, vacuum_cleanup_index_scale_factor)}, {"deduplicate_items", RELOPT_TYPE_BOOL, offsetof(BTOptions, deduplicate_items)} }; return (bytea *) build_reloptions(reloptions, validate, RELOPT_KIND_BTREE, sizeof(BTOptions), tab, lengthof(tab)); } /* * btproperty() -- Check boolean properties of indexes. * * This is optional, but handling AMPROP_RETURNABLE here saves opening the rel * to call btcanreturn. */ bool btproperty(Oid index_oid, int attno, IndexAMProperty prop, const char *propname, bool *res, bool *isnull) { switch (prop) { case AMPROP_RETURNABLE: /* answer only for columns, not AM or whole index */ if (attno == 0) return false; /* otherwise, btree can always return data */ *res = true; return true; default: return false; /* punt to generic code */ } } /* * btbuildphasename() -- Return name of index build phase. */ char * btbuildphasename(int64 phasenum) { switch (phasenum) { case PROGRESS_CREATEIDX_SUBPHASE_INITIALIZE: return "initializing"; case PROGRESS_BTREE_PHASE_INDEXBUILD_TABLESCAN: return "scanning table"; case PROGRESS_BTREE_PHASE_PERFORMSORT_1: return "sorting live tuples"; case PROGRESS_BTREE_PHASE_PERFORMSORT_2: return "sorting dead tuples"; case PROGRESS_BTREE_PHASE_LEAF_LOAD: return "loading tuples in tree"; default: return NULL; } } /* * _bt_truncate() -- create tuple without unneeded suffix attributes. * * Returns truncated pivot index tuple allocated in caller's memory context, * with key attributes copied from caller's firstright argument. If rel is * an INCLUDE index, non-key attributes will definitely be truncated away, * since they're not part of the key space. More aggressive suffix * truncation can take place when it's clear that the returned tuple does not * need one or more suffix key attributes. We only need to keep firstright * attributes up to and including the first non-lastleft-equal attribute. * Caller's insertion scankey is used to compare the tuples; the scankey's * argument values are not considered here. * * Note that returned tuple's t_tid offset will hold the number of attributes * present, so the original item pointer offset is not represented. Caller * should only change truncated tuple's downlink. Note also that truncated * key attributes are treated as containing "minus infinity" values by * _bt_compare(). * * In the worst case (when a heap TID must be appended to distinguish lastleft * from firstright), the size of the returned tuple is the size of firstright * plus the size of an additional MAXALIGN()'d item pointer. This guarantee * is important, since callers need to stay under the 1/3 of a page * restriction on tuple size. If this routine is ever taught to truncate * within an attribute/datum, it will need to avoid returning an enlarged * tuple to caller when truncation + TOAST compression ends up enlarging the * final datum. */ IndexTuple _bt_truncate(Relation rel, IndexTuple lastleft, IndexTuple firstright, BTScanInsert itup_key) { TupleDesc itupdesc = RelationGetDescr(rel); int16 nkeyatts = IndexRelationGetNumberOfKeyAttributes(rel); int keepnatts; IndexTuple pivot; IndexTuple tidpivot; ItemPointer pivotheaptid; Size newsize; /* * We should only ever truncate non-pivot tuples from leaf pages. It's * never okay to truncate when splitting an internal page. */ Assert(!BTreeTupleIsPivot(lastleft) && !BTreeTupleIsPivot(firstright)); /* Determine how many attributes must be kept in truncated tuple */ keepnatts = _bt_keep_natts(rel, lastleft, firstright, itup_key); #ifdef DEBUG_NO_TRUNCATE /* Force truncation to be ineffective for testing purposes */ keepnatts = nkeyatts + 1; #endif pivot = index_truncate_tuple(itupdesc, firstright, Min(keepnatts, nkeyatts)); if (BTreeTupleIsPosting(pivot)) { /* * index_truncate_tuple() just returns a straight copy of firstright * when it has no attributes to truncate. When that happens, we may * need to truncate away a posting list here instead. */ Assert(keepnatts == nkeyatts || keepnatts == nkeyatts + 1); Assert(IndexRelationGetNumberOfAttributes(rel) == nkeyatts); pivot->t_info &= ~INDEX_SIZE_MASK; pivot->t_info |= MAXALIGN(BTreeTupleGetPostingOffset(firstright)); } /* * If there is a distinguishing key attribute within pivot tuple, we're * done */ if (keepnatts <= nkeyatts) { BTreeTupleSetNAtts(pivot, keepnatts, false); return pivot; } /* * We have to store a heap TID in the new pivot tuple, since no non-TID * key attribute value in firstright distinguishes the right side of the * split from the left side. nbtree conceptualizes this case as an * inability to truncate away any key attributes, since heap TID is * treated as just another key attribute (despite lacking a pg_attribute * entry). * * Use enlarged space that holds a copy of pivot. We need the extra space * to store a heap TID at the end (using the special pivot tuple * representation). Note that the original pivot already has firstright's * possible posting list/non-key attribute values removed at this point. */ newsize = MAXALIGN(IndexTupleSize(pivot)) + MAXALIGN(sizeof(ItemPointerData)); tidpivot = palloc0(newsize); memcpy(tidpivot, pivot, MAXALIGN(IndexTupleSize(pivot))); /* Cannot leak memory here */ pfree(pivot); /* * Store all of firstright's key attribute values plus a tiebreaker heap * TID value in enlarged pivot tuple */ tidpivot->t_info &= ~INDEX_SIZE_MASK; tidpivot->t_info |= newsize; BTreeTupleSetNAtts(tidpivot, nkeyatts, true); pivotheaptid = BTreeTupleGetHeapTID(tidpivot); /* * Lehman & Yao use lastleft as the leaf high key in all cases, but don't * consider suffix truncation. It seems like a good idea to follow that * example in cases where no truncation takes place -- use lastleft's heap * TID. (This is also the closest value to negative infinity that's * legally usable.) */ ItemPointerCopy(BTreeTupleGetMaxHeapTID(lastleft), pivotheaptid); /* * We're done. Assert() that heap TID invariants hold before returning. * * Lehman and Yao require that the downlink to the right page, which is to * be inserted into the parent page in the second phase of a page split be * a strict lower bound on items on the right page, and a non-strict upper * bound for items on the left page. Assert that heap TIDs follow these * invariants, since a heap TID value is apparently needed as a * tiebreaker. */ #ifndef DEBUG_NO_TRUNCATE Assert(ItemPointerCompare(BTreeTupleGetMaxHeapTID(lastleft), BTreeTupleGetHeapTID(firstright)) < 0); Assert(ItemPointerCompare(pivotheaptid, BTreeTupleGetHeapTID(lastleft)) >= 0); Assert(ItemPointerCompare(pivotheaptid, BTreeTupleGetHeapTID(firstright)) < 0); #else /* * Those invariants aren't guaranteed to hold for lastleft + firstright * heap TID attribute values when they're considered here only because * DEBUG_NO_TRUNCATE is defined (a heap TID is probably not actually * needed as a tiebreaker). DEBUG_NO_TRUNCATE must therefore use a heap * TID value that always works as a strict lower bound for items to the * right. In particular, it must avoid using firstright's leading key * attribute values along with lastleft's heap TID value when lastleft's * TID happens to be greater than firstright's TID. */ ItemPointerCopy(BTreeTupleGetHeapTID(firstright), pivotheaptid); /* * Pivot heap TID should never be fully equal to firstright. Note that * the pivot heap TID will still end up equal to lastleft's heap TID when * that's the only usable value. */ ItemPointerSetOffsetNumber(pivotheaptid, OffsetNumberPrev(ItemPointerGetOffsetNumber(pivotheaptid))); Assert(ItemPointerCompare(pivotheaptid, BTreeTupleGetHeapTID(firstright)) < 0); #endif return tidpivot; } /* * _bt_keep_natts - how many key attributes to keep when truncating. * * Caller provides two tuples that enclose a split point. Caller's insertion * scankey is used to compare the tuples; the scankey's argument values are * not considered here. * * This can return a number of attributes that is one greater than the * number of key attributes for the index relation. This indicates that the * caller must use a heap TID as a unique-ifier in new pivot tuple. */ static int _bt_keep_natts(Relation rel, IndexTuple lastleft, IndexTuple firstright, BTScanInsert itup_key) { int nkeyatts = IndexRelationGetNumberOfKeyAttributes(rel); TupleDesc itupdesc = RelationGetDescr(rel); int keepnatts; ScanKey scankey; /* * _bt_compare() treats truncated key attributes as having the value minus * infinity, which would break searches within !heapkeyspace indexes. We * must still truncate away non-key attribute values, though. */ if (!itup_key->heapkeyspace) return nkeyatts; scankey = itup_key->scankeys; keepnatts = 1; for (int attnum = 1; attnum <= nkeyatts; attnum++, scankey++) { Datum datum1, datum2; bool isNull1, isNull2; datum1 = index_getattr(lastleft, attnum, itupdesc, &isNull1); datum2 = index_getattr(firstright, attnum, itupdesc, &isNull2); if (isNull1 != isNull2) break; if (!isNull1 && DatumGetInt32(FunctionCall2Coll(&scankey->sk_func, scankey->sk_collation, datum1, datum2)) != 0) break; keepnatts++; } /* * Assert that _bt_keep_natts_fast() agrees with us in passing. This is * expected in an allequalimage index. */ Assert(!itup_key->allequalimage || keepnatts == _bt_keep_natts_fast(rel, lastleft, firstright)); return keepnatts; } /* * _bt_keep_natts_fast - fast bitwise variant of _bt_keep_natts. * * This is exported so that a candidate split point can have its effect on * suffix truncation inexpensively evaluated ahead of time when finding a * split location. A naive bitwise approach to datum comparisons is used to * save cycles. * * The approach taken here usually provides the same answer as _bt_keep_natts * will (for the same pair of tuples from a heapkeyspace index), since the * majority of btree opclasses can never indicate that two datums are equal * unless they're bitwise equal after detoasting. When an index only has * "equal image" columns, routine is guaranteed to give the same result as * _bt_keep_natts would. * * Callers can rely on the fact that attributes considered equal here are * definitely also equal according to _bt_keep_natts, even when the index uses * an opclass or collation that is not "allequalimage"/deduplication-safe. * This weaker guarantee is good enough for nbtsplitloc.c caller, since false * negatives generally only have the effect of making leaf page splits use a * more balanced split point. */ int _bt_keep_natts_fast(Relation rel, IndexTuple lastleft, IndexTuple firstright) { TupleDesc itupdesc = RelationGetDescr(rel); int keysz = IndexRelationGetNumberOfKeyAttributes(rel); int keepnatts; keepnatts = 1; for (int attnum = 1; attnum <= keysz; attnum++) { Datum datum1, datum2; bool isNull1, isNull2; CompactAttribute *att; datum1 = index_getattr(lastleft, attnum, itupdesc, &isNull1); datum2 = index_getattr(firstright, attnum, itupdesc, &isNull2); att = TupleDescCompactAttr(itupdesc, attnum - 1); if (isNull1 != isNull2) break; if (!isNull1 && !datum_image_eq(datum1, datum2, att->attbyval, att->attlen)) break; keepnatts++; } return keepnatts; } /* * _bt_check_natts() -- Verify tuple has expected number of attributes. * * Returns value indicating if the expected number of attributes were found * for a particular offset on page. This can be used as a general purpose * sanity check. * * Testing a tuple directly with BTreeTupleGetNAtts() should generally be * preferred to calling here. That's usually more convenient, and is always * more explicit. Call here instead when offnum's tuple may be a negative * infinity tuple that uses the pre-v11 on-disk representation, or when a low * context check is appropriate. This routine is as strict as possible about * what is expected on each version of btree. */ bool _bt_check_natts(Relation rel, bool heapkeyspace, Page page, OffsetNumber offnum) { int16 natts = IndexRelationGetNumberOfAttributes(rel); int16 nkeyatts = IndexRelationGetNumberOfKeyAttributes(rel); BTPageOpaque opaque = BTPageGetOpaque(page); IndexTuple itup; int tupnatts; /* * We cannot reliably test a deleted or half-dead page, since they have * dummy high keys */ if (P_IGNORE(opaque)) return true; Assert(offnum >= FirstOffsetNumber && offnum <= PageGetMaxOffsetNumber(page)); itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum)); tupnatts = BTreeTupleGetNAtts(itup, rel); /* !heapkeyspace indexes do not support deduplication */ if (!heapkeyspace && BTreeTupleIsPosting(itup)) return false; /* Posting list tuples should never have "pivot heap TID" bit set */ if (BTreeTupleIsPosting(itup) && (ItemPointerGetOffsetNumberNoCheck(&itup->t_tid) & BT_PIVOT_HEAP_TID_ATTR) != 0) return false; /* INCLUDE indexes do not support deduplication */ if (natts != nkeyatts && BTreeTupleIsPosting(itup)) return false; if (P_ISLEAF(opaque)) { if (offnum >= P_FIRSTDATAKEY(opaque)) { /* * Non-pivot tuple should never be explicitly marked as a pivot * tuple */ if (BTreeTupleIsPivot(itup)) return false; /* * Leaf tuples that are not the page high key (non-pivot tuples) * should never be truncated. (Note that tupnatts must have been * inferred, even with a posting list tuple, because only pivot * tuples store tupnatts directly.) */ return tupnatts == natts; } else { /* * Rightmost page doesn't contain a page high key, so tuple was * checked above as ordinary leaf tuple */ Assert(!P_RIGHTMOST(opaque)); /* * !heapkeyspace high key tuple contains only key attributes. Note * that tupnatts will only have been explicitly represented in * !heapkeyspace indexes that happen to have non-key attributes. */ if (!heapkeyspace) return tupnatts == nkeyatts; /* Use generic heapkeyspace pivot tuple handling */ } } else /* !P_ISLEAF(opaque) */ { if (offnum == P_FIRSTDATAKEY(opaque)) { /* * The first tuple on any internal page (possibly the first after * its high key) is its negative infinity tuple. Negative * infinity tuples are always truncated to zero attributes. They * are a particular kind of pivot tuple. */ if (heapkeyspace) return tupnatts == 0; /* * The number of attributes won't be explicitly represented if the * negative infinity tuple was generated during a page split that * occurred with a version of Postgres before v11. There must be * a problem when there is an explicit representation that is * non-zero, or when there is no explicit representation and the * tuple is evidently not a pre-pg_upgrade tuple. * * Prior to v11, downlinks always had P_HIKEY as their offset. * Accept that as an alternative indication of a valid * !heapkeyspace negative infinity tuple. */ return tupnatts == 0 || ItemPointerGetOffsetNumber(&(itup->t_tid)) == P_HIKEY; } else { /* * !heapkeyspace downlink tuple with separator key contains only * key attributes. Note that tupnatts will only have been * explicitly represented in !heapkeyspace indexes that happen to * have non-key attributes. */ if (!heapkeyspace) return tupnatts == nkeyatts; /* Use generic heapkeyspace pivot tuple handling */ } } /* Handle heapkeyspace pivot tuples (excluding minus infinity items) */ Assert(heapkeyspace); /* * Explicit representation of the number of attributes is mandatory with * heapkeyspace index pivot tuples, regardless of whether or not there are * non-key attributes. */ if (!BTreeTupleIsPivot(itup)) return false; /* Pivot tuple should not use posting list representation (redundant) */ if (BTreeTupleIsPosting(itup)) return false; /* * Heap TID is a tiebreaker key attribute, so it cannot be untruncated * when any other key attribute is truncated */ if (BTreeTupleGetHeapTID(itup) != NULL && tupnatts != nkeyatts) return false; /* * Pivot tuple must have at least one untruncated key attribute (minus * infinity pivot tuples are the only exception). Pivot tuples can never * represent that there is a value present for a key attribute that * exceeds pg_index.indnkeyatts for the index. */ return tupnatts > 0 && tupnatts <= nkeyatts; } /* * * _bt_check_third_page() -- check whether tuple fits on a btree page at all. * * We actually need to be able to fit three items on every page, so restrict * any one item to 1/3 the per-page available space. Note that itemsz should * not include the ItemId overhead. * * It might be useful to apply TOAST methods rather than throw an error here. * Using out of line storage would break assumptions made by suffix truncation * and by contrib/amcheck, though. */ void _bt_check_third_page(Relation rel, Relation heap, bool needheaptidspace, Page page, IndexTuple newtup) { Size itemsz; BTPageOpaque opaque; itemsz = MAXALIGN(IndexTupleSize(newtup)); /* Double check item size against limit */ if (itemsz <= BTMaxItemSize) return; /* * Tuple is probably too large to fit on page, but it's possible that the * index uses version 2 or version 3, or that page is an internal page, in * which case a slightly higher limit applies. */ if (!needheaptidspace && itemsz <= BTMaxItemSizeNoHeapTid) return; /* * Internal page insertions cannot fail here, because that would mean that * an earlier leaf level insertion that should have failed didn't */ opaque = BTPageGetOpaque(page); if (!P_ISLEAF(opaque)) elog(ERROR, "cannot insert oversized tuple of size %zu on internal page of index \"%s\"", itemsz, RelationGetRelationName(rel)); ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), errmsg("index row size %zu exceeds btree version %u maximum %zu for index \"%s\"", itemsz, needheaptidspace ? BTREE_VERSION : BTREE_NOVAC_VERSION, needheaptidspace ? BTMaxItemSize : BTMaxItemSizeNoHeapTid, RelationGetRelationName(rel)), errdetail("Index row references tuple (%u,%u) in relation \"%s\".", ItemPointerGetBlockNumber(BTreeTupleGetHeapTID(newtup)), ItemPointerGetOffsetNumber(BTreeTupleGetHeapTID(newtup)), RelationGetRelationName(heap)), errhint("Values larger than 1/3 of a buffer page cannot be indexed.\n" "Consider a function index of an MD5 hash of the value, " "or use full text indexing."), errtableconstraint(heap, RelationGetRelationName(rel)))); } /* * Are all attributes in rel "equality is image equality" attributes? * * We use each attribute's BTEQUALIMAGE_PROC opclass procedure. If any * opclass either lacks a BTEQUALIMAGE_PROC procedure or returns false, we * return false; otherwise we return true. * * Returned boolean value is stored in index metapage during index builds. * Deduplication can only be used when we return true. */ bool _bt_allequalimage(Relation rel, bool debugmessage) { bool allequalimage = true; /* INCLUDE indexes can never support deduplication */ if (IndexRelationGetNumberOfAttributes(rel) != IndexRelationGetNumberOfKeyAttributes(rel)) return false; for (int i = 0; i < IndexRelationGetNumberOfKeyAttributes(rel); i++) { Oid opfamily = rel->rd_opfamily[i]; Oid opcintype = rel->rd_opcintype[i]; Oid collation = rel->rd_indcollation[i]; Oid equalimageproc; equalimageproc = get_opfamily_proc(opfamily, opcintype, opcintype, BTEQUALIMAGE_PROC); /* * If there is no BTEQUALIMAGE_PROC then deduplication is assumed to * be unsafe. Otherwise, actually call proc and see what it says. */ if (!OidIsValid(equalimageproc) || !DatumGetBool(OidFunctionCall1Coll(equalimageproc, collation, ObjectIdGetDatum(opcintype)))) { allequalimage = false; break; } } if (debugmessage) { if (allequalimage) elog(DEBUG1, "index \"%s\" can safely use deduplication", RelationGetRelationName(rel)); else elog(DEBUG1, "index \"%s\" cannot use deduplication", RelationGetRelationName(rel)); } return allequalimage; }