| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: NOT DEFERRABLE vs. DEFERRABLE INITIALLY IMMEDIATE constraints |
| Date: | 2014-02-06 19:46:02 |
| Message-ID: | 23474.1391715962@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
Jeff Janes <jeff(dot)janes(at)gmail(dot)com> writes:
> I've been plagued several times by NOT DEFERRABLE constraints. Is there
> any good reason to define a constraint as NOT DEFERRABLE rather
> than DEFERRABLE INITIALLY IMMEDIATE? For example, is there performance
> penalty for PostgreSQL being prepared to defer a constraint even though it
> is not currently being deferred?
There's a substantial performance difference between deferrable and
nondeferrable uniqueness constraints (ie, indexes). For foreign keys
I don't believe it matters. We don't implement deferrability for
other types of constraints such as CHECK.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Merlin Moncure | 2014-02-06 19:54:17 | Re: Offending My Tender Sensibilities -OR- OLTP on a Star Schema |
| Previous Message | Jeff Janes | 2014-02-06 19:26:03 | NOT DEFERRABLE vs. DEFERRABLE INITIALLY IMMEDIATE constraints |