Re: Bucket and batch

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> "Ana Carolina Brito de Almeida" <anacrl(at)ig(dot)com(dot)br> writes:
>> So, I would like to know the differences between bucket and batch.
>
> A bucket is, well, one bucket of a hash table --- it holds all the
> tuples that have the same hash code (for as many bits of the hash
> code as we are choosing to use). We try to size the hash table with
> enough buckets so there's not more than 10 tuples per bucket on
> average.
>
> A batch is a range of buckets that we process at the same time.

Note that we don't currently do batches for hash aggregates, only joins
currently.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning