Re: PostgreSQL Query Speed Issues

On Thu, Feb 21, 2013 at 3:56 PM, Joseph Pravato
<joseph(dot)pravato(at)nomagic(dot)com> wrote:
> NOTE: All database tests were done without changing or updating any settings after install.

The defaults are sub-optimal. You really do need to tune them to the
server in question.

>
> # rows in contact: 574939
> # rows in contact_address_map: 574924

After loading this data, did you run an ANALYZE?

> select c.*
> from contact c
> left join CONTACT_ADDRESS_MAP cam on cam.CONTACT_ID = c.id
> where cam.ADDRESS_ID is null

Table definitions would probably help. You might be missing indexes.

>
> Result from an 'explain analyze':
>
> QUERY PLAN
> Merge Left Join (cost=83512.87..158059.12 rows=1 width=952) (actual time=5224.171..5224.270 rows=15 loops=1)
> Merge Cond: (c.id = cam.contact_id)
> Filter: (cam.address_id IS NULL)
> Rows Removed by Filter: 574924
> -> Index Scan using contact_pkey on contact c (cost=0.00..63048.48 rows=574917 width=952) (actual time=0.009..852.708 rows=574939 loops=1)
> -> Materialize (cost=83512.59..86387.17 rows=574917 width=16) (actual time=1407.387..3107.246 rows=574924 loops=1)
> -> Sort (cost=83512.59..84949.88 rows=574917 width=16) (actual time=1407.379..2027.946 rows=574924 loops=1)
> Sort Key: cam.contact_id
> Sort Method: external sort Disk: 14616kB

disk sorts imply work_mem isn't big enough.

> -> Seq Scan on contact_address_map cam (cost=0.00..8857.17 rows=574917 width=16) (actual time=0.018..578.348 rows=574924 loops=1)

This should probably be using an index

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