From: Christoph Haller <ch@rodos.fzk.de>
To: tomas@nocrew.org
Cc: pgsql-sql@postgresql.org
Subject: Re: Big query problem
Date: Fri, 29 Nov 2002 10:55:21 +0100
Message-ID: <3DE73988.F29C6A6E@rodos.fzk.de> (raw)
>
> DELETE FROM table WHERE col1='something' AND col2 IN
> ('aasdoijhfoisdfsdoif','sdfsdfsdfsadfsdf', ... );
>
> In the parantheses I have 6400 names, each about 20 characters. I'm
> using libpq from C. This did not work very well, but the result was
> very unexpected.
>
The conditional operator IN is or at least was known to be slow.
Did you think of an alternative approach as
CREATE TABLE to_delete_col2 ( ref_col2 ... ) ;
populate it with 'aasdoijhfoisdfsdoif','sdfsdfsdfsadfsdf', ...
and then
DELETE FROM table WHERE col1='something' AND
EXISTS (SELECT ref_col2 FROM to_delete_col2 WHERE table.col2 =
to_delete_col2.ref_col2 );
> My application has several threads, each opening its own connection to
> the database. The above query was run in a transaction followed by a
> COMMIT. There was no error from running the above query, but instead,
> it seems that the query was never run at all. As a side effect, every
> other connection to the database always got:
>
> NOTICE: current transaction is aborted, queries ignored until end of
> transaction block
>
> when trying to run a query. I thought that the transactions in
> different connections didn't have anything to do with each other.
>
>
> If I limited the number of names in the failing query to 3200, it
> worked well and as expected.
>
>
> Is there a limit in libpq of the length of a query? And if this is
> exceeded, shouldn't PQexec() give an error?
I agree!
>
I think you should post this to the HACKERS list. Maybe you'll get
a reply from there.
Regards, Christoph
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To: pgsql-sql@postgresql.org
Cc: ch@rodos.fzk.de, tomas@nocrew.org
Subject: Re: Big query problem
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