Re: HAVING push-down

Simon Riggs wrote:
> On Fri, 2007-01-26 at 15:22 +0000, Gregory Stark wrote:
>> "Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
>>
>>> I've just read a paper that says PostgreSQL doesn't do this. My reading
>>> of the code is that we *do* evaluate the HAVING clause prior to
>>> calculating the aggregates for it. I thought I'd check to resolve the
>>> confusion.
>>>
>
>> You mean in cases like this?
>>
>> postgres=# explain select count(*) from customer group by c_w_id,c_d_id,c_id having c_w_id = 1 and c_d_id=1 and c_id=1;
>> QUERY PLAN
>> ------------------------------------------------------------------------------------
>> GroupAggregate (cost=0.00..13.61 rows=1 width=12)
>> -> Index Scan using pk_customer on customer (cost=0.00..13.56 rows=4 width=12)
>> Index Cond: ((c_w_id = 1) AND (c_d_id = 1) AND (c_id = 1))
>> (3 rows)
>
> OK, thanks. I'll feedback to the author of the paper I was reviewing.
>

Care to share the paper in general? It might be beneficial for all of us.

Joshua D. Drake

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