From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Jacky Leng <lengjianquan(at)163(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Why copy_relation_data only use wal whenWALarchivingis enabled |
Date: | 2007-10-17 17:13:14 |
Message-ID: | 471642AA.9010306@enterprisedb.com |
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Lists: | pgsql-hackers pgsql-patches |
Tom Lane wrote:
> Simon has a legitimate objection; not that there's no bug, but that the
> probability of getting bitten is exceedingly small.
Oh, if that's what he meant, he's right.
> The test script you
> showed cheats six-ways-from-Sunday to cause an OID collision that would
> never happen in practice. The only case where it would really happen
> is if a table that has existed for a long time (~ 2^32 OID creations)
> gets dropped and then you're unlucky enough to recycle that exact OID
> before the next checkpoint --- and then crash before the checkpoint.
Yeah, it's unlikely to happen, but the consequences are horrible.
Note that it's not just DROP TABLE that's a problem, but anything that
uses smgrscheduleunlink, including CLUSTER and REINDEX.
> I tend to agree that truncating the file, and extending the fsync
> request mechanism to actually delete it after the next checkpoint,
> is the most reasonable route to a fix.
Ok, I'll write a patch to do that.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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