| From: | "Mikheev, Vadim" <vmikheev(at)SECTORBASE(dot)COM> |
|---|---|
| To: | "'sygma(at)marr(dot)irisz(dot)hu'" <sygma(at)marr(dot)irisz(dot)hu>, "'pgsql-bugs(at)postgresql(dot)org'" <pgsql-bugs(at)postgresql(dot)org> |
| Cc: | "'janwieck(at)Yahoo(dot)com'" <janwieck(at)Yahoo(dot)com>, "'pgsql-hackers(at)postgresql(dot)org'" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | RE: foreign key check makes a big LOCK |
| Date: | 2000-12-05 20:59:50 |
| Message-ID: | 8F4C99C66D04D4118F580090272A7A234D31CC@sectorbase1.sectorbase.com |
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| Thread: | |
| Lists: | pgsql-bugs pgsql-hackers |
> Short Description
> foreign key check makes a big LOCK
>
> Long Description
> in: src/backend/utils/adt/ri_triggers.c
>
> RI_FKey_check(), RI_FKey_noaction_upd(), RI_FKey_noaction_del(), etc..
> checking the referential with SELECT FOR UPDATE.
>
> After BEGIN TRANSACTION: the INSERT/DELETE/UPDATE calling
> foreign-key checks, and the SELECT FOR UPDATE locking ALL
> matched rows in referential table.
>
> I modify ri_triggers.c (remove "FOR UPDATE"). This working..
> but is correct?
It's not. If one transaction inserts FK 1 and another one deletes
PK 1 at the same time both will succeed.
RI triggers should perform dirty reads (and test if returned tuples
alive/dead/being updated by concurrent transaction) instead of
SELECT FOR UPDATE but dirty reads are not implemented, yet.
Vadim
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