From: Alexander Korotkov <akorotkov@postgresql.org>
Date: Tue, 19 Nov 2019 20:08:14 +0000 (+0300)
Subject: Fix traversing to the deleted GIN page via downlink
X-Git-Url: http://git.postgresql.org/gitweb/-?a=commitdiff_plain;h=d5ad7a09afd066dce423f282bb2b338f48614d32;p=users%2Fc2main%2Fpostgres.git

Fix traversing to the deleted GIN page via downlink

Current GIN code appears to don't handle traversing to the deleted page via
downlink.  This commit fixes that by stepping right from the delete page like
we do in nbtree.

This commit also fixes setting 'deleted' flag to the GIN pages.  Now other page
flags are not erased once page is deleted.  That helps to keep our assertions
true if we arrive deleted page via downlink.

Discussion: https://postgr.es/m/CAPpHfdvMvsw-NcE5bRS7R1BbvA4BxoDnVVjkXC5W0Czvy9LVrg%40mail.gmail.com
Author: Alexander Korotkov
Reviewed-by: Peter Geoghegan
Backpatch-through: 9.4
---

diff --git a/src/backend/access/gin/ginbtree.c b/src/backend/access/gin/ginbtree.c
index 20adfa2194..8f8cd85db6 100644
--- a/src/backend/access/gin/ginbtree.c
+++ b/src/backend/access/gin/ginbtree.c
@@ -187,13 +187,6 @@ ginStepRight(Buffer buffer, Relation index, int lockmode)
 	if (isLeaf != GinPageIsLeaf(page) || isData != GinPageIsData(page))
 		elog(ERROR, "right sibling of GIN page is of different type");
 
-	/*
-	 * Given the proper lock sequence above, we should never land on a deleted
-	 * page.
-	 */
-	if (GinPageIsDeleted(page))
-		elog(ERROR, "right sibling of GIN page was deleted");
-
 	return nextbuffer;
 }
 
diff --git a/src/backend/access/gin/gindatapage.c b/src/backend/access/gin/gindatapage.c
index e8c34d6b1f..e497210b4c 100644
--- a/src/backend/access/gin/gindatapage.c
+++ b/src/backend/access/gin/gindatapage.c
@@ -238,6 +238,9 @@ dataIsMoveRight(GinBtree btree, Page page)
 	if (GinPageRightMost(page))
 		return false;
 
+	if (GinPageIsDeleted(page))
+		return true;
+
 	return (ginCompareItemPointers(&btree->itemptr, iptr) > 0) ? true : false;
 }
 
diff --git a/src/backend/access/gin/ginvacuum.c b/src/backend/access/gin/ginvacuum.c
index 85acddc76b..3a695a0555 100644
--- a/src/backend/access/gin/ginvacuum.c
+++ b/src/backend/access/gin/ginvacuum.c
@@ -186,7 +186,7 @@ ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkn
 	 * we shouldn't change rightlink field to save workability of running
 	 * search scan
 	 */
-	GinPageGetOpaque(page)->flags = GIN_DELETED;
+	GinPageSetDeleted(page);
 
 	MarkBufferDirty(pBuffer);
 	MarkBufferDirty(lBuffer);
diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c
index c945b28272..387102f21a 100644
--- a/src/backend/access/gin/ginxlog.c
+++ b/src/backend/access/gin/ginxlog.c
@@ -500,7 +500,7 @@ ginRedoDeletePage(XLogReaderState *record)
 	{
 		page = BufferGetPage(dbuffer);
 		Assert(GinPageIsData(page));
-		GinPageGetOpaque(page)->flags = GIN_DELETED;
+		GinPageSetDeleted(page);
 		GinPageSetDeleteXid(page, data->deleteXid);
 		PageSetLSN(page, lsn);
 		MarkBufferDirty(dbuffer);