From 796962922e6938fdad4dbf810fb2a5dfcfc5f45a Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: 2025年9月12日 13:23:00 -0400 Subject: [PATCH] Always commute strategy when preprocessing DESC keys. A recently added nbtree preprocessing step failed to account for the fact that DESC columns already had their B-Tree strategy number commuted at this point in preprocessing. As a result, preprocessing could output a set of scan keys where one or more keys had the correct strategy number, but used the wrong comparison routine. To fix, make the faulty code path that looks up a more restrictive replacement operator/comparison routine commute its requested inequality strategy (while outputting the transformed strategy number as before). This makes the final transformed scan key comport with the approach preprocessing has always used to deal with DESC columns (which is described by comments above _bt_fix_scankey_strategy). Oversight in commit commit b3f1a13f, which made nbtree preprocessing perform transformations on skip array inequalities that can reduce the total number of index searches. Author: Peter Geoghegan Reported-By: Natalya Aksman Discussion: https://postgr.es/m/19049-b7df801e71de41b2@postgresql.org Backpatch-through: 18 --- src/backend/access/nbtree/nbtpreprocesskeys.c | 24 ++++++++++++++----- 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/src/backend/access/nbtree/nbtpreprocesskeys.c b/src/backend/access/nbtree/nbtpreprocesskeys.c index 936b93f157a..07a3ff11a0b 100644 --- a/src/backend/access/nbtree/nbtpreprocesskeys.c +++ b/src/backend/access/nbtree/nbtpreprocesskeys.c @@ -1412,6 +1412,7 @@ _bt_skiparray_strat_decrement(IndexScanDesc scan, ScanKey arraysk, Datum orig_sk_argument = high_compare->sk_argument, new_sk_argument; bool uflow; + int16 lookupstrat; Assert(high_compare->sk_strategy == BTLessStrategyNumber); @@ -1433,9 +1434,14 @@ _bt_skiparray_strat_decrement(IndexScanDesc scan, ScanKey arraysk, return; } - /* Look up <= operator (might fail) */ - leop = get_opfamily_member(opfamily, opcintype, opcintype, - BTLessEqualStrategyNumber); + /* + * Look up <= operator (might fail), accounting for the fact that a + * high_compare on a DESC column already had its strategy commuted + */ + lookupstrat = BTLessEqualStrategyNumber; + if (high_compare->sk_flags & SK_BT_DESC) + lookupstrat = BTGreaterEqualStrategyNumber; /* commute this too */ + leop = get_opfamily_member(opfamily, opcintype, opcintype, lookupstrat); if (!OidIsValid(leop)) return; cmp_proc = get_opcode(leop); @@ -1464,6 +1470,7 @@ _bt_skiparray_strat_increment(IndexScanDesc scan, ScanKey arraysk, Datum orig_sk_argument = low_compare->sk_argument, new_sk_argument; bool oflow; + int16 lookupstrat; Assert(low_compare->sk_strategy == BTGreaterStrategyNumber); @@ -1485,9 +1492,14 @@ _bt_skiparray_strat_increment(IndexScanDesc scan, ScanKey arraysk, return; } - /* Look up>= operator (might fail) */ - geop = get_opfamily_member(opfamily, opcintype, opcintype, - BTGreaterEqualStrategyNumber); + /* + * Look up>= operator (might fail), accounting for the fact that a + * low_compare on a DESC column already had its strategy commuted + */ + lookupstrat = BTGreaterEqualStrategyNumber; + if (low_compare->sk_flags & SK_BT_DESC) + lookupstrat = BTLessEqualStrategyNumber; /* commute this too */ + geop = get_opfamily_member(opfamily, opcintype, opcintype, lookupstrat); if (!OidIsValid(geop)) return; cmp_proc = get_opcode(geop); -- 2.39.5

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