From f801783ade88e524b73acfa19f1b06e5b54608df Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Fri, 10 May 2024 03:07:53 +0300 Subject: [PATCH v3 1/4] amcheck: Optimize speed of checking for unique constraint violation Currently, when amcheck validates a unique constraint, it visits the heap for each index tuple. This commit implements skipping keys, which have only one non-dedeuplicated index tuple (quite common case for unique indexes). That gives substantial economy on index checking time. Reported-by: Noah Misch Discussion: https://postgr.es/m/20240325020323.fd.nmisch%40google.com Author: Alexander Korotkov, Pavel Borisov --- contrib/amcheck/verify_nbtree.c | 35 +++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c index 70f65b645a6..c7be785f88b 100644 --- a/contrib/amcheck/verify_nbtree.c +++ b/contrib/amcheck/verify_nbtree.c @@ -1429,6 +1429,13 @@ bt_target_page_check(BtreeCheckState *state) bool lowersizelimit; ItemPointer scantid; + /* + * True if we already called bt_entry_unique_check() for the current + * item. This helps to avoid visiting the heap for keys, which are + * anyway presented only once and can't comprise a unique violation. + */ + bool unique_checked = false; + CHECK_FOR_INTERRUPTS(); itemid = PageGetItemIdCareful(state, state->targetblock, @@ -1771,13 +1778,19 @@ bt_target_page_check(BtreeCheckState *state) /* * If the index is unique verify entries uniqueness by checking the - * heap tuples visibility. + * heap tuples visibility. Immediately check posting tuples and + * tuples with repeated keys. Postpone check for keys, which have the + * first appearance. */ if (state->checkunique && state->indexinfo->ii_Unique && - P_ISLEAF(topaque) && !skey->anynullkeys) + P_ISLEAF(topaque) && !skey->anynullkeys && + (BTreeTupleIsPosting(itup) || ItemPointerIsValid(lVis_tid))) + { bt_entry_unique_check(state, itup, state->targetblock, offset, &lVis_i, &lVis_tid, &lVis_offset, &lVis_block); + unique_checked = true; + } if (state->checkunique && state->indexinfo->ii_Unique && P_ISLEAF(topaque) && OffsetNumberNext(offset) <= max) @@ -1796,6 +1809,9 @@ bt_target_page_check(BtreeCheckState *state) * data (whole index tuple or last posting in index tuple). Key * containing null value does not violate unique constraint and * treated as different to any other key. + * + * If the next key is the same as the previous one, do the + * bt_entry_unique_check() call if it was postponed. */ if (_bt_compare(state->rel, skey, state->target, OffsetNumberNext(offset)) != 0 || skey->anynullkeys) @@ -1805,6 +1821,12 @@ bt_target_page_check(BtreeCheckState *state) lVis_block = InvalidBlockNumber; lVis_offset = InvalidOffsetNumber; } + else if (!unique_checked) + { + bt_entry_unique_check(state, itup, state->targetblock, offset, + &lVis_i, &lVis_tid, &lVis_offset, + &lVis_block); + } skey->scantid = scantid; /* Restore saved scan key state */ } @@ -1889,6 +1911,15 @@ bt_target_page_check(BtreeCheckState *state) /* The first key on the next page is the same */ if (_bt_compare(state->rel, rightkey, state->target, max) == 0 && !rightkey->anynullkeys) { + /* + * Do the bt_entry_unique_check() call if it was + * postponed. + */ + if (!unique_checked) + bt_entry_unique_check(state, itup, state->targetblock, offset, + &lVis_i, &lVis_tid, &lVis_offset, + &lVis_block); + elog(DEBUG2, "cross page equal keys"); state->target = palloc_btree_page(state, rightblock_number); -- 2.39.3 (Apple Git-145)