From 9c6a676c4cedab50e4015f49c871dbcdfc4efe07 Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Thu, 19 Jul 2018 21:04:17 +0300 Subject: Fix handling of empty uncompressed posting list pages in GIN PostgreSQL 9.4 introduces posting list compression in GIN. This feature supports online upgrade, so that after pg_upgrade uncompressed posting lists are compressed on-the-fly. Underlying code appears to always expect at least one item on uncompressed posting list page. But there could be completely empty pages, because VACUUM never deletes leftmost and rightmost pages from posting trees. This commit fixes that. Reported-by: Sivasubramanian Ramasubramanian Discussion: https://postgr.es/m/1531867212836.63354%40amazon.com Author: Sivasubramanian Ramasubramanian, Alexander Korotkov Backpatch-through: 9.4 --- src/backend/access/gin/ginxlog.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) (limited to 'src/backend/access/gin/ginxlog.c') diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c index 7f93ce6526f..130ee7d5b2c 100644 --- a/src/backend/access/gin/ginxlog.c +++ b/src/backend/access/gin/ginxlog.c @@ -160,15 +160,30 @@ ginRedoRecompress(Page page, ginxlogRecompressDataLeaf *data) ItemPointer uncompressed = (ItemPointer) GinDataPageGetData(page); int nuncompressed = GinPageGetOpaque(page)->maxoff; int npacked; - GinPostingList *plist; - plist = ginCompressPostingList(uncompressed, nuncompressed, - BLCKSZ, &npacked); - Assert(npacked == nuncompressed); + /* + * Empty leaf pages are deleted as part of vacuum, but leftmost and + * rightmost pages are never deleted. So, pg_upgrade'd from pre-9.4 + * instances might contain empty leaf pages, and we need to handle + * them correctly. + */ + if (nuncompressed > 0) + { + GinPostingList *plist; + + plist = ginCompressPostingList(uncompressed, nuncompressed, + BLCKSZ, &npacked); + totalsize = SizeOfGinPostingList(plist); + + Assert(npacked == nuncompressed); - totalsize = SizeOfGinPostingList(plist); + memcpy(GinDataLeafPageGetPostingList(page), plist, totalsize); + } + else + { + totalsize = 0; + } - memcpy(GinDataLeafPageGetPostingList(page), plist, totalsize); GinDataPageSetDataSize(page, totalsize); GinPageSetCompressed(page); GinPageGetOpaque(page)->maxoff = InvalidOffsetNumber; -- cgit v1.2.3