Re: [HACKERS] execGrouping.c limit on work_mem

2017-05-28 Thread Tom Lane 
Jeff Janes  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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[HACKERS] execGrouping.c limit on work_mem

2017-05-27 Thread Jeff Janes 
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.

Also:

* false if it existed already.  ->additional_data in the new entry has

The field is just ->additional, not ->additional_data

Cheers,

Jeff