| From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
|---|---|
| To: | Gregory Stark <stark(at)enterprisedb(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndQuadrant(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Hot standby and b-tree killed items |
| Date: | 2008-12-20 07:25:27 |
| Message-ID: | 494C9DE7.1060505@enterprisedb.com |
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| Lists: | pgsql-hackers |
Heikki Linnakangas wrote:
> Gregory Stark wrote:
>> The question I had was whether your solution for btree pointers marked
>> dead
>> and later dropped from the index works when the user hasn't configured a
>> timeout and doesn't want standby queries killed.
>
> Yes, it's not any different from vacuum WAL records.
No wait, there is a nasty corner-case. When an index tuple is marked as
killed, no WAL record is written. Since there's now WAL record, it won't
be killed in the slave yet. But if we take a full-page image of that
page later for some other operation, the LP_DEAD flag is included in the
full-page image. If the flag sneaks into the slave without an explicit
WAL record like that, there's no latestRemovedXid for the slave to wait on.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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