Re: [HACKERS] execGrouping.c limit on work_mem - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [HACKERS] execGrouping.c limit on work_mem
Date
Msg-id 21217.1495993748@sss.pgh.pa.us
Whole thread Raw
In response to [HACKERS] execGrouping.c limit on work_mem  (Jeff Janes <jeff.janes@gmail.com>)
List pgsql-hackers
Jeff Janes <jeff.janes@gmail.com> writes:
> In BuildTupleHashTable
>     /* Limit initial table size request to not more than work_mem */
>     nbuckets = Min(nbuckets, (long) ((work_mem * 1024L) / entrysize));

> Is this a good idea?  If the caller of this code has no respect for
> work_mem, they are still going to blow it out of the water.  Now we will
> just do a bunch of hash-table splitting in the process.  That is only going
> to add to the pain.

It looks perfectly reasonable to me.  The point I think is that the caller
doesn't have to be very careful about calculating its initial request
size.
        regards, tom lane



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