From: Simon Riggs <simon@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
To: Karim Nassar <karim.nassar@NAU.EDU>
Cc: Christopher Kings-Lynne <chriskl@familyhealth.com.au>
Cc: pgsql-performance@postgresql.org
Subject: Re: Delete query takes exorbitant amount of time
Date: Fri, 25 Mar 2005 15:10:48 +0000
Message-ID: <1111763448.11750.730.camel@localhost.localdomain> (raw)
In-Reply-To: <20845.1111733900@sss.pgh.pa.us>
References: <1111709457.9085.127.camel@k2.cet.nau.edu>
<2630.1111711927@sss.pgh.pa.us>
<1111715131.9085.174.camel@k2.cet.nau.edu>
<3750.1111715318@sss.pgh.pa.us>
<4243879B.10200@familyhealth.com.au>
<20845.1111733900@sss.pgh.pa.us>
On Fri, 2005-03-25 at 01:58 -0500, Tom Lane wrote:
> Christopher Kings-Lynne <chriskl@familyhealth.com.au> writes:
> >> In that case there's a datatype mismatch between the referencing and
> >> referenced columns, which prevents the index from being used for the
> >> FK check.
>
> > Is creating such a foreign key a WARNING yet?
>
> I believe so as of 8.0. It's a bit tricky since 8.0 does allow some
> cross-type cases to be indexed, but IIRC we have a test that understands
> about that...
src/backend/commands/tablecmds.c, line 3966 in CVSTIP
/*
* Check that the found operator is compatible with the PK index,
* and generate a warning if not, since otherwise costly seqscans
* will be incurred to check FK validity.
*/
if (!op_in_opclass(oprid(o), opclasses[i]))
ereport(WARNING,
(errmsg("foreign key constraint \"%s\" "
"will require costly sequential scans",
fkconstraint->constr_name),
errdetail("Key columns \"%s\" and \"%s\" "
"are of different types: %s and %s.",
strVal(list_nth(fkconstraint->fk_attrs, i)),
strVal(list_nth(fkconstraint->pk_attrs, i)),
format_type_be(fktypoid[i]),
format_type_be(pktypoid[i]))));
So, yes to the WARNING. Not sure about the cross-type cases...
Karim: Did this happen? If not, can you drop and re-create and confirm
that you get the WARNING? If not, we have problems.
I vote to make this an ERROR in 8.1 - I see little benefit in allowing
this situation to continue. If users do create a FK like this, it just
becomes another performance problem on list...
Best Regards, Simon Riggs
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To: pgsql-performance@postgresql.org
Cc: simon@2ndquadrant.com, tgl@sss.pgh.pa.us, karim.nassar@NAU.EDU, chriskl@familyhealth.com.au
Subject: Re: Delete query takes exorbitant amount of time
In-Reply-To: <1111763448.11750.730.camel@localhost.localdomain>
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