| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Jeff Davis <pgsql(at)j-davis(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, npboley(at)gmail(dot)com |
| Subject: | Re: More FOR UPDATE/FOR SHARE problems |
| Date: | 2009-02-03 03:04:32 |
| Message-ID: | 200902030304.n1334Ww18548@momjian.us |
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| Lists: | pgsql-hackers |
Bruce Momjian wrote:
> The fundamental behavior above is that the S1 transaction is adding
> _and_ removing rows from the S2 query's result set; S2 is seeing the
> pre-query values that don't match its criteria and ignoring them and
> blocking on a later row that does match its criteria. Once S1 commits,
> the new row does not match its criteria and it skips it, making the
> SELECT FOR UPDATE return zero rows, and the S2 UPDATE do nothing.
>
> Serializable mode does prevent the problem outlined above.
To clarify, serializable throws an error, as expected.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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