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Fix race introduced by 6d46f4783e.

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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.
This commit is contained in:
Robert Haas 2016-12-05 11:43:37 -05:00
parent 0e50af2453
commit 2f4193c350
1 changed files with 11 additions and 3 deletions
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14
src/backend/access/hash/hashpage.c
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@ -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);