From: Tom Lane <tgl@sss.pgh.pa.us>
To: mario.splivalo@mobart.hr
Cc: pgsql-sql@postgresql.org
Subject: Re: Slow query - SELECTing one row from 'big' table.
Date: Thu, 03 Nov 2005 10:17:35 -0500
Message-ID: <22145.1131031055@sss.pgh.pa.us> (raw)
In-Reply-To: <1131026341.18615.20.camel@ekim>
References: <1131026341.18615.20.camel@ekim>
Mario Splivalo <mario.splivalo@mobart.hr> writes:
> SELECT *
> FROM messages
> WHERE (id = currval(''public.message_id_seq''::text))
That cannot legally be converted into an indexscan, because currval() is
a volatile function --- the planner cannot be certain that its value
won't change during the query. (In this case we can assume it's safe
because nothing in that query would call nextval(), but the planner
isn't omniscient enough to make that conclusion.)
Fetch the currval into a local variable and use the variable in the
query.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, mario.splivalo@mobart.hr
Subject: Re: Slow query - SELECTing one row from 'big' table.
In-Reply-To: <22145.1131031055@sss.pgh.pa.us>
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