From: Scott Carey <scott@richrelevance.com>
To: "dan@sidhe.org" <dan@sidhe.org>, Alvaro Herrera
	<alvherre@commandprompt.com>
CC: Robert Haas <robertmhaas@gmail.com>, Scott Marlowe
	<scott.marlowe@gmail.com>, "pgsql-performance@postgresql.org"
	<pgsql-performance@postgresql.org>
Date: Mon, 30 Mar 2009 14:44:50 -0700
Subject: Re: Trying to track down weird query stalls
Thread-Topic: [PERFORM] Trying to track down weird query stalls
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On 3/30/09 2:34 PM, "dan@sidhe.org" <dan@sidhe.org> wrote:

>> dan@sidhe.org escribi=F3:
>>=20
>>>> So what's the "?" in the query you pasted earlier?
>>>=20
>>> The first ? (for architecture) is 1, the second ? (for branchid) is 0.
>>> They both should get passed to Postgres as $1 and $2, respectively,
>>> assuming DBD::Pg does its substitution right. (They're both supposed to
>>> go
>>> in as placeholders)
>>=20
>> Right, so how about you reread what I wrote above?
>>=20
>> Oh, hmm, so to be more clear: I don't think DBD::Pg is actually sending
>> EXECUTE PREPARE.  You need to do this over psql.
>=20
> Fair enough. (And sorry about the mis-read) Next time this occurs I'll tr=
y
> and duplicate this in psql. FWIW, a quick read of the C underlying the
> DBD::Pg module shows it using PQexecPrepared, so I'm pretty sure it is
> using prepared statements with placeholders, but double-checking seems
> prudent.
>=20
> -Dan
>=20

Regardless, its always a good idea to do a manual explain analyze with and
without parameterization in psql if prepared statements are involved.  The
query planner functions very differently with and without them, almost
always with a performance detriment to query execution times when
parameterized.