From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)heroku(dot)com> |
Subject: | Re: assertion failure 9.3.4 |
Date: | 2014-04-21 16:14:26 |
Message-ID: | 535543E2.9020404@agliodbs.com |
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Lists: | pgsql-hackers |
All,
1) I've confirmed at the 2nd site that the issue doesn't happen if
pg_stat_statements.so is not loaded. So this seems to be confirmation
that either auto_explain, pg_stat_statements, or both need to be loaded
(but not necessarily created as extensions) in order to have the issue.
2) I've been unable to reproduce the issue using a naive test case, but
I'll keep trying.
3) The XID information is interesting.
a) I've confirmed that this is a case of having multiple row versions
rather than allowing a duplicate PK to be inserted.
b) the end result of this corruption is XIDs which go backwards:
xmin | xmax | ctid | step_id | workitem_id | status
---------+---------+-----------+---------+-------------+---------
3362707 | 3362707 | (6177,31) | 1 | 446469 | pending
3362710 | 3362707 | (6177,32) | 1 | 446469 | working
5520953 | 5520953 | (5064,105) | 1 | 727946 | pending
5520954 | 5520953 | (5064,108) | 1 | 727946 | working
What's additionally problematic is that the current snapshot minxid is
in the 9000000 range, so it's not clear why any of the above rows are
visible at all.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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