Re: RI_FKey_check: foreign key constraint blocks parall

> > > void
> > > heap_mark4fk_lock_acquire(Relation relation, HeapTuple tuple) {

Just wonder how are you going to implement it - is it by using
some kind of "read-locks", ie FK transaction "locks" PK to prevent
delete (this is known as "pessimistic" approach)?
About two years ago we discussed with Jan "optimistic" approach
with using "dirty reads", when PK/FK transactions do not check
existence of FK/PK untill constraint should be checked (after
statement processed for immediate mode, at the commit time/
set constraint immediate for deferred constraints).

So, at the check time, FK transaction uses dirty reads to know
about existence/"status" of PK:
1. No PK -> abort.
2. PK (inserted?/)deleted/updated/selected for update by concurrent
transaction P -> wait for P commit/abort (just like transactions do
for concurrent same-row-update); go to 1.
3. Else (PK exists and no one changing it right now) -> proceed.

PK transaction does the same:
1. No FK -> proceed.
2. FK inserted/updated/selected for update by concurrent transaction
F -> wait for F commit/abort; go to 1.

This would be more in MVCC style -:)

Vadim