From 93cd7684ee2bba227fa371daa81b88f25456dcb2 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 3 Apr 2017 22:24:17 -0400
Subject: [PATCH] Properly acquire buffer lock for page-at-a-time hash vacuum.
In a couple of places, _hash_kill_items was mistakenly called with
the buffer lock not held. Repair.
Ashutosh Sharma, per a report from Andreas Seltenreich
Discussion: http://postgr.es/m/87o9wo8o0j.fsf@credativ.de
---
src/backend/access/hash/hash.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/src/backend/access/hash/hash.c b/src/backend/access/hash/hash.c
index 34cc08f12d2..b835f772d46 100644
--- a/src/backend/access/hash/hash.c
+++ b/src/backend/access/hash/hash.c
@@ -476,9 +476,17 @@ hashrescan(IndexScanDesc scan, ScanKey scankey, int nscankeys,
HashScanOpaque so = (HashScanOpaque) scan->opaque;
Relation rel = scan->indexRelation;
- /* Before leaving current page, deal with any killed items */
+ /*
+ * Before leaving current page, deal with any killed items.
+ * Also, ensure that we acquire lock on current page before
+ * calling _hash_kill_items.
+ */
if (so->numKilled > 0)
+ {
+ LockBuffer(so->hashso_curbuf, BUFFER_LOCK_SHARE);
_hash_kill_items(scan);
+ LockBuffer(so->hashso_curbuf, BUFFER_LOCK_UNLOCK);
+ }
_hash_dropscanbuf(rel, so);
@@ -507,9 +515,17 @@ hashendscan(IndexScanDesc scan)
HashScanOpaque so = (HashScanOpaque) scan->opaque;
Relation rel = scan->indexRelation;
- /* Before leaving current page, deal with any killed items */
+ /*
+ * Before leaving current page, deal with any killed items.
+ * Also, ensure that we acquire lock on current page before
+ * calling _hash_kill_items.
+ */
if (so->numKilled > 0)
+ {
+ LockBuffer(so->hashso_curbuf, BUFFER_LOCK_SHARE);
_hash_kill_items(scan);
+ LockBuffer(so->hashso_curbuf, BUFFER_LOCK_UNLOCK);
+ }
_hash_dropscanbuf(rel, so);
--
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