| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: unlogged tables |
| Date: | 2010-12-15 09:20:41 |
| Message-ID: | 1292404841.2737.5749.camel@ebony |
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| Thread: | |
| Lists: | pgsql-hackers |
On Sat, 2010-11-13 at 19:16 -0500, Robert Haas wrote:
> 3. The third patch (relax-sync-commit-v1) allows asynchronous commit
> even when synchronous_commit=on if the transaction has not written
> WAL. Of course, a read-only transaction won't even have an XID and
> therefore won't need a commit record, so what this is really doing is
> allowing transactions that have written only to temp - or unlogged -
> tables to commit asynchronously.
I like this, great idea.
Avoiding the commit record entirely will break Hot Standby though, since
we rely on the assumption that all xids that are assigned are also
logged. The xids would be "known assigned", yet since they never
actually appear they will clog up the machinery (pun unintended).
--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services
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