From 2f4193c3509a822c55cc0eae77e7788806d9b022 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Mon, 5 Dec 2016 11:43:37 -0500 Subject: [PATCH] Fix race introduced by 6d46f4783efe457f74816a75173eb23ed8930020. It's possible for the metapage contents to change after we release the lock, so we must read them before releasing the lock. Amit Kapila. Submitted in response to a trouble report from Andreas Seltenreich, though it is not certain this fixes the problem. --- src/backend/access/hash/hashpage.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/src/backend/access/hash/hashpage.c b/src/backend/access/hash/hashpage.c index 74ffa9d161..44332e72ec 100644 --- a/src/backend/access/hash/hashpage.c +++ b/src/backend/access/hash/hashpage.c @@ -653,13 +653,21 @@ restart_expand: */ if (H_NEEDS_SPLIT_CLEANUP(oopaque)) { + /* + * Copy bucket mapping info now; refer to the comment in code below + * where we copy this information before calling _hash_splitbucket + * to see why this is okay. + */ + maxbucket = metap->hashm_maxbucket; + highmask = metap->hashm_highmask; + lowmask = metap->hashm_lowmask; + /* Release the metapage lock. */ _hash_chgbufaccess(rel, metabuf, HASH_READ, HASH_NOLOCK); hashbucketcleanup(rel, old_bucket, buf_oblkno, start_oblkno, NULL, - metap->hashm_maxbucket, metap->hashm_highmask, - metap->hashm_lowmask, NULL, - NULL, true, NULL, NULL); + maxbucket, highmask, lowmask, NULL, NULL, true, + NULL, NULL); _hash_dropbuf(rel, buf_oblkno);