> 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