Re: [INTERFACES] Postmaster getting veeeery big: SUBSTR bug - Mailing list pgsql-interfaces

From Tom Lane
Subject Re: [INTERFACES] Postmaster getting veeeery big: SUBSTR bug
Date
Msg-id 954.927145744@sss.pgh.pa.us
Whole thread Raw
In response to Postmaster getting veeeery big: SUBSTR bug  (Eildert Groeneveld <eg@tzv.fal.de>)
List pgsql-interfaces
Eildert Groeneveld <eg@tzv.fal.de> writes:
> Herouth was right in stating: "memory used for substr function" has to be
> the real cause of the problem because any substr select exhibits this
> behaviour:
> select substr(tets,1,2) from raw_field; 
> This one starts the postmaster at around 3MB and finishes at 40.
> Unfortunately, I have no idea about C, can someone identify the problem
> and come up with a patch?

The problem is well known and is on the TO-DO list: memory consumed
while evaluating expressions is not reclaimed until end of statement.
It's by no means specific to substr().

Unfortunately, fixing it is not a small amount of work (else it'd have
been done already).  I'm hoping to see it fixed in 6.6.
        regards, tom lane


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