| From: | Neil Conway <neilc(at)samurai(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: locks in CREATE TRIGGER, ADD FK |
| Date: | 2005-03-23 04:26:37 |
| Message-ID: | 4240EFFD.4090805@samurai.com |
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| Lists: | pgsql-hackers |
Tom Lane wrote:
> Utterly wrong. When you commit you will physically drop the old table.
> If there is a SELECT running against the old table it will be quite
> unhappy after that.
How can we drop the file at commit, given that a serializable
transaction's snapshot should still be able to see old relfilenode's
content?
(If the serializable transaction has already acquired a read lock before
the TRUNCATE begins, it will block the TRUNCATE -- but there is no
guarantee that the operations will be ordered like that.)
-Neil
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