| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Dave Page" <dpage(at)vale-housing(dot)co(dot)uk> |
| Cc: | "PostgreSQL Hackers Mailing List" <pgsql-hackers(at)postgresql(dot)org>, "Didier Moens" <moensd(at)xs4all(dot)be> |
| Subject: | Re: Foreign key wierdness |
| Date: | 2003-01-20 15:27:38 |
| Message-ID: | 3113.1043076458@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"Dave Page" <dpage(at)vale-housing(dot)co(dot)uk> writes:
> A pgAdmin user has noticed that Foreign Keys take significantly longer
> to create when migrating a database in pgAdmin in v1.4.12 than in
> v1.4.2.
The only reason ADD FOREIGN KEY would take a long time is if
(a) it has to wait awhile to get exclusive lock on either
the referencing or referenced table; and/or
(b) it takes a long time to verify that the existing entries
in the referencing table all have matches in the referenced table.
(that's the behind-the-scenes query you see)
I'm betting that the table was busy, or there was a lot more data
present in the one case, or you hadn't ever vacuumed/analyzed one or
both tables and so a bad plan was chosen for the verification query.
The schema reference is definitely not the issue.
regards, tom lane
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