From 324ab164ef7e32dd40e120bc22a79711a82cd77b Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Fri, 10 May 2024 03:07:53 +0300 Subject: [PATCH v4] 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 | 36 ++++++++++++++++++++++++++++++--- 1 file changed, 33 insertions(+), 3 deletions(-) diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c index 34990c5cea3..7cfb136763f 100644 --- a/contrib/amcheck/verify_nbtree.c +++ b/contrib/amcheck/verify_nbtree.c @@ -1433,6 +1433,13 @@ 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, @@ -1775,12 +1782,18 @@ 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); + unique_checked = true; + } if (state->checkunique && state->indexinfo->ii_Unique && P_ISLEAF(topaque) && OffsetNumberNext(offset) <= max) @@ -1799,6 +1812,9 @@ 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) @@ -1808,6 +1824,11 @@ bt_target_page_check(BtreeCheckState *state) lVis.postingIndex = -1; lVis.tid = NULL; } + else if (!unique_checked) + { + bt_entry_unique_check(state, itup, state->targetblock, offset, + &lVis); + } skey->scantid = scantid; /* Restore saved scan key state */ } @@ -1890,10 +1911,19 @@ bt_target_page_check(BtreeCheckState *state) rightkey->scantid = NULL; /* The first key on the next page is the same */ - if (_bt_compare(state->rel, rightkey, state->target, max) == 0 && !rightkey->anynullkeys) + if (_bt_compare(state->rel, rightkey, state->target, max) == 0 && + !rightkey->anynullkeys) { Page rightpage; + /* + * Do the bt_entry_unique_check() call if it was + * postponed. + */ + if (!unique_checked) + bt_entry_unique_check(state, itup, state->targetblock, + offset, &lVis); + elog(DEBUG2, "cross page equal keys"); rightpage = palloc_btree_page(state, rightblock_number); -- 2.39.3 (Apple Git-145)