From e9041f10384250472a54bd75a1cf28f89ec15e32 Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Mon, 13 May 2024 04:18:56 +0300 Subject: [PATCH v3 3/4] amcheck: Don't load the right sibling page into BtreeCheckState 5ae2087202 implemented a cross-page unique constraint check by loading the right sibling to the BtreeCheckState.target variable. This is wrong, because bt_target_page_check() shouldn't change the target page. Also, BtreeCheckState.target shouldn't be changed alone without BtreeCheckState.targetblock. However, the above didn't cause any visible bugs for the following reasons. 1. We do a cross-page unique constraint check only for leaf index pages. 2. The only way target page get accessed after a cross-page unique constraint check is loading of the lowkey. 3. The only place lowkey is used is bt_child_highkey_check(), and that applies only to non-leafs. The reasons above don't diminish the fact that changing BtreeCheckState.target for a cross-page unique constraint check is wrong. This commit changes this check to temporarily store the right sibling to the local variable. Reported-by: Peter Geoghegan Discussion: https://postgr.es/m/CAH2-Wzk%2B2116uOXdOViA27SHcr31WKPgmjsxXLBs_aTxAeThzg%40mail.gmail.com Author: Pavel Borisov --- contrib/amcheck/verify_nbtree.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c index b433cb33254..977f8b6799d 100644 --- a/contrib/amcheck/verify_nbtree.c +++ b/contrib/amcheck/verify_nbtree.c @@ -1910,6 +1910,8 @@ 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) { + Page rightpage; + /* * Do the bt_entry_unique_check() call if it was * postponed. @@ -1918,19 +1920,21 @@ bt_target_page_check(BtreeCheckState *state) bt_entry_unique_check(state, itup, state->targetblock, offset, &lVis); elog(DEBUG2, "cross page equal keys"); - state->target = palloc_btree_page(state, - rightblock_number); - topaque = BTPageGetOpaque(state->target); + rightpage = palloc_btree_page(state, + rightblock_number); + topaque = BTPageGetOpaque(rightpage); if (P_IGNORE(topaque) || !P_ISLEAF(topaque)) break; itemid = PageGetItemIdCareful(state, rightblock_number, - state->target, + rightpage, rightfirstoffset); - itup = (IndexTuple) PageGetItem(state->target, itemid); + itup = (IndexTuple) PageGetItem(rightpage, itemid); bt_entry_unique_check(state, itup, rightblock_number, rightfirstoffset, &lVis); + + pfree(rightpage); } } } -- 2.39.3 (Apple Git-145)