From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 11 Apr 2017 16:03:12 +0000 (-0400)
Subject: Fix failure when a shared tidbitmap has only one page.
X-Git-Tag: REL_10_BETA1~302
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4c3b59abf4c476843bca23de7fb66d647627f30e;p=postgresql

Fix failure when a shared tidbitmap has only one page.

Commit 98e6e89040a0534ca26914c66cae9dd49ef62ad9 made inadequate
provision for the case of a single-page shared tidbitmap.  It
allocate space for a shared PagetableEntry, but failed to
initialize it.

Report by Thomas Munro.  Patch by Dilip Kumar, with some comment
changes by me.

Discussion: http://postgr.es/m/CAEepm=19Cmnfbi-j2Bw-a6yGPeHE1OVhKvvKz9bRBTJGKfGHMA@mail.gmail.com
---

diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index eab8f68356..c66019e3ba 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -866,12 +866,14 @@ tbm_prepare_shared_iterate(TIDBitmap *tbm)
 		else if (tbm->status == TBM_ONE_PAGE)
 		{
 			/*
-			 * In one page mode allocate the space for one pagetable entry and
-			 * directly store its index i.e. 0 in page array
+			 * In one page mode allocate the space for one pagetable entry,
+			 * initialize it, and directly store its index (i.e. 0) in the
+			 * page array.
 			 */
 			tbm->dsapagetable = dsa_allocate(tbm->dsa, sizeof(PTEntryArray) +
 											 sizeof(PagetableEntry));
 			ptbase = dsa_get_address(tbm->dsa, tbm->dsapagetable);
+			memcpy(ptbase->ptentry, &tbm->entry1, sizeof(PagetableEntry));
 			ptpages->index[0] = 0;
 		}