From f47b5e139579a77c1f7c63400f01ea39d515e8c8 Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Wed, 5 Aug 2020 02:15:34 +0300 Subject: [PATCH] Remove btree page items after page unlink Currently, page unlink leaves remaining items "as is", but replay of corresponding WAL-record re-initializes page leaving it with no items. For the sake of consistency, this commit makes primary delete all the items during page unlink as well. Thanks to this change, we now don't mask contents of deleted btree page for WAL consistency checking. Discussion: https://postgr.es/m/CAPpHfdt_OTyQpXaPJcWzV2N-LNeNJseNB-K_A66qG%3DL518VTFw%40mail.gmail.com Author: Alexander Korotkov Reviewed-by: Peter Geoghegan --- contrib/amcheck/verify_nbtree.c | 7 ++----- src/backend/access/nbtree/nbtpage.c | 9 +++++++++ src/backend/access/nbtree/nbtxlog.c | 10 +--------- 3 files changed, 12 insertions(+), 14 deletions(-) diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c index e4d501a85d..c9f9e755dc 100644 --- a/contrib/amcheck/verify_nbtree.c +++ b/contrib/amcheck/verify_nbtree.c @@ -2864,11 +2864,8 @@ palloc_btree_page(BtreeCheckState *state, BlockNumber blocknum) * As noted at the beginning of _bt_binsrch(), an internal page must have * children, since there must always be a negative infinity downlink * (there may also be a highkey). In the case of non-rightmost leaf - * pages, there must be at least a highkey. Deleted pages on replica - * might contain no items, because page unlink re-initializes - * page-to-be-deleted. Deleted pages with no items might be on primary - * too due to preceding recovery, but on primary new deletions can't - * happen concurrently to amcheck. + * pages, there must be at least a highkey. The exceptions are deleted + * pages, which contain no items. * * This is correct when pages are half-dead, since internal pages are * never half-dead, and leaf pages must have a high key when half-dead diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c index 53dff32680..d5db9aaa3a 100644 --- a/src/backend/access/nbtree/nbtpage.c +++ b/src/backend/access/nbtree/nbtpage.c @@ -2058,6 +2058,7 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, BlockNumber scanblkno, BTMetaPageData *metad = NULL; ItemId itemid; Page page; + PageHeader header; BTPageOpaque opaque; bool rightsib_is_rightmost; int targetlevel; @@ -2327,6 +2328,14 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, BlockNumber scanblkno, opaque->btpo_flags |= BTP_DELETED; opaque->btpo.xact = ReadNewTransactionId(); + /* + * Remove the remaining tuples on the page. This keeps things simple for + * WAL consistency checking. + */ + header = (PageHeader) page; + header->pd_lower = SizeOfPageHeaderData; + header->pd_upper = header->pd_special; + /* And update the metapage, if needed */ if (BufferIsValid(metabuf)) { diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c index 09d1b0e341..be0fa450f3 100644 --- a/src/backend/access/nbtree/nbtxlog.c +++ b/src/backend/access/nbtree/nbtxlog.c @@ -1051,15 +1051,7 @@ btree_mask(char *pagedata, BlockNumber blkno) maskopaq = (BTPageOpaque) PageGetSpecialPointer(page); - if (P_ISDELETED(maskopaq)) - { - /* - * Mask page content on a DELETED page since it will be re-initialized - * during replay. See btree_xlog_unlink_page() for details. - */ - mask_page_content(page); - } - else if (P_ISLEAF(maskopaq)) + if (P_ISLEAF(maskopaq)) { /* * In btree leaf pages, it is possible to modify the LP_FLAGS without