From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Craig James <cjames(at)emolecules(dot)com>, Massalin Yerzhan <yerzhik(at)gmail(dot)com>, postgres performance list <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Simple delete query is taking too long (never ends) |
Date: | 2015-11-13 14:15:06 |
Message-ID: | CAHyXU0xAp_dJXU+c-6dmjrrOS8ijWRKuj_S4mAGGOP_AyzhYbg@mail.gmail.com |
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Lists: | pgsql-performance |
On Thu, Nov 12, 2015 at 4:26 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
>> On Thu, Nov 12, 2015 at 9:48 AM, Craig James <cjames(at)emolecules(dot)com> wrote:
>>> What about a warning on creation?
>>>
>>> db=> create table foo(i integer primary key);
>>> db=> create table bar(j integer primary key, i integer);
>>> db=> alter table bar add constraint fk_bar foreign key(i) references foo(i);
>>> WARNING: fk_bar: column bar(i) has no index, deletions on table foo may be
>>> slow.
>>>
>>> It might save some fraction of these questions.
>
>> Maybe, but I wonder if this would cause pg_restore to bleat warnings
>> when restoring.
>
> We could probably teach pg_dump to put index definitions before FKs, if it
> doesn't already. But I'm suspicious of this sort of "training wheels"
> warning --- we've had roughly similar messages in the past and removed
> them because too many people complained about them.
For posterity, indexes are the last step -- and I think that's a good
way to do things. As to the broader point, I agree. Warnings should
be reserved for things that are demonstrably dubious, and there are
just too many situations where that doesn't apply for an unindexed
foreign constraint. Oh well.
merlin
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