diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/nbtree/nbtsearch.c | 67 |
1 files changed, 60 insertions, 7 deletions
diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c index f4bea8cd537..d48936bed6d 100644 --- a/src/backend/access/nbtree/nbtsearch.c +++ b/src/backend/access/nbtree/nbtsearch.c @@ -456,6 +456,7 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) bool goback; ScanKey startKeys[INDEX_MAX_KEYS]; ScanKeyData scankeys[INDEX_MAX_KEYS]; + ScanKeyData notnullkeys[INDEX_MAX_KEYS]; int keysCount = 0; int i; StrategyNumber strat_total; @@ -506,6 +507,14 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) * one we use --- by definition, they are either redundant or * contradictory. * + * Any regular (not SK_SEARCHNULL) key implies a NOT NULL qualifier. + * If the index stores nulls at the end of the index we'll be starting + * from, and we have no boundary key for the column (which means the key + * we deduced NOT NULL from is an inequality key that constrains the other + * end of the index), then we cons up an explicit SK_SEARCHNOTNULL key to + * use as a boundary key. If we didn't do this, we might find ourselves + * traversing a lot of null entries at the start of the scan. + * * In this loop, row-comparison keys are treated the same as keys on their * first (leftmost) columns. We'll add on lower-order columns of the row * comparison below, if possible. @@ -519,6 +528,7 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) { AttrNumber curattr; ScanKey chosen; + ScanKey impliesNN; ScanKey cur; /* @@ -528,6 +538,8 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) */ curattr = 1; chosen = NULL; + /* Also remember any scankey that implies a NOT NULL constraint */ + impliesNN = NULL; /* * Loop iterates from 0 to numberOfKeys inclusive; we use the last @@ -540,8 +552,32 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) { /* * Done looking at keys for curattr. If we didn't find a - * usable boundary key, quit; else save the boundary key - * pointer in startKeys. + * usable boundary key, see if we can deduce a NOT NULL key. + */ + if (chosen == NULL && impliesNN != NULL && + ((impliesNN->sk_flags & SK_BT_NULLS_FIRST) ? + ScanDirectionIsForward(dir) : + ScanDirectionIsBackward(dir))) + { + /* Yes, so build the key in notnullkeys[keysCount] */ + chosen = ¬nullkeys[keysCount]; + ScanKeyEntryInitialize(chosen, + (SK_SEARCHNOTNULL | SK_ISNULL | + (impliesNN->sk_flags & + (SK_BT_DESC | SK_BT_NULLS_FIRST))), + curattr, + ((impliesNN->sk_flags & SK_BT_NULLS_FIRST) ? + BTGreaterStrategyNumber : + BTLessStrategyNumber), + InvalidOid, + InvalidOid, + InvalidOid, + (Datum) 0); + } + + /* + * If we still didn't find a usable boundary key, quit; else + * save the boundary key pointer in startKeys. */ if (chosen == NULL) break; @@ -574,15 +610,27 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) */ curattr = cur->sk_attno; chosen = NULL; + impliesNN = NULL; } - /* Can we use this key as a starting boundary for this attr? */ + /* + * Can we use this key as a starting boundary for this attr? + * + * If not, does it imply a NOT NULL constraint? (Because + * SK_SEARCHNULL keys are always assigned BTEqualStrategyNumber, + * *any* inequality key works for that; we need not test.) + */ switch (cur->sk_strategy) { case BTLessStrategyNumber: case BTLessEqualStrategyNumber: - if (chosen == NULL && ScanDirectionIsBackward(dir)) - chosen = cur; + if (chosen == NULL) + { + if (ScanDirectionIsBackward(dir)) + chosen = cur; + else + impliesNN = cur; + } break; case BTEqualStrategyNumber: /* override any non-equality choice */ @@ -590,8 +638,13 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) break; case BTGreaterEqualStrategyNumber: case BTGreaterStrategyNumber: - if (chosen == NULL && ScanDirectionIsForward(dir)) - chosen = cur; + if (chosen == NULL) + { + if (ScanDirectionIsForward(dir)) + chosen = cur; + else + impliesNN = cur; + } break; } } |