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Re: Speeding up query, Joining 55mil and 43mil records.

From: "Dave Dutcher" <dave(at)tridecap(dot)com>
To: "'nicky'" <nicky(at)valuecare(dot)nl>,<pgsql-performance(at)postgresql(dot)org>
Subject: Re: Speeding up query, Joining 55mil and 43mil records.
Date: 2006-06-21 14:53:03
Message-ID: 00cb01c69542$663f1c30$ (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Could you post an explain analyze of the query?  Just FYI, if you do an
explain analyze of the insert statement, it will actually do the insert.
If you don't want that just post an explain analyze of the select part.
To me it would be interesting to compare just the select parts of the
query between Postgres and MSSQL.  That way you would know if your
Postgres install is slower at the query or slower at the insert.

-----Original Message-----
From: pgsql-performance-owner(at)postgresql(dot)org
[mailto:pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of nicky
Sent: Wednesday, June 21, 2006 8:47 AM
To: pgsql-performance(at)postgresql(dot)org
Subject: [PERFORM] Speeding up query, Joining 55mil and 43mil records. 

Hello People, 

I'm trying to solve a 'what i feel is a' performance/configuration/query
error on my side. I'm fairly new to configuring PostgreSQL so, i might
be completely wrong with my configuration. 

My database consists of 44 tables, about 20GB. Two of those tables are
'big/huge'. Table src.src_faktuur_verricht contains 43million records
(9GB) and table src.src_faktuur_verrsec contains 55million records

Below is the 'slow' query. 

INSERT INTO rpt.rpt_verrichting
,       t0.secid
,       t1.status
,       t1.patientnr
,       t1.datum
,       t1.locatie
,       t1.afdeling
,       t1.uitvoerder
,       t1.aanvrager
,       t0.code
,       t1.casenr
,       t0.aantal
,       t0.kostplaats
,       null
,       null
,       null
FROM    src.src_faktuur_verrsec t0 JOIN
        src.src_faktuur_verricht t1 ON =
WHERE   substr(t0.code,1,2) not in ('14','15','16','17')
AND     (substr(t0.correctie,4,1) <> '1' OR t0.correctie is null)
AND     EXTRACT(YEAR from t1.datum) > 2004;

Output from explain

Hash Join  (cost=1328360.12..6167462.76 rows=7197568 width=118)
  Hash Cond: (("outer".id)::text = ("inner".id)::text)

  ->  Seq Scan on src_faktuur_verrsec t0  (cost=0.00..2773789.90
rows=40902852 width=52)
        Filter: ((substr((code)::text, 1, 2) <> '14'::text) AND
(substr((code)::text, 1, 2) <> '15'::text) AND (substr((code)::text, 1,
2) <> '16'::text) AND (substr((code)::text, 1, 2) <> '17'::text) AND
((substr((correctie)::text, 4, 1) <> '1'::text) OR (correctie IS NULL)))
  ->  Hash  (cost=1188102.97..1188102.97 rows=8942863 width=80)
        ->  Bitmap Heap Scan on src_faktuur_verricht t1
(cost=62392.02..1188102.97 rows=8942863 width=80)
              Recheck Cond: (date_part('year'::text, datum) >
2004::double precision)
              ->  Bitmap Index Scan on src_faktuur_verricht_idx1
(cost=0.00..62392.02 rows=8942863 width=0)
                    Index Cond: (date_part('year'::text, datum) >
2004::double precision)

The db server runs PostgreSQL 8.1.4 on FreeBSD 6.1-Stable. 2GB of RAM. 
It contains two SATA150 disks, one contains PostgreSQL and the rest of
the operating system and the other disk holds the pg_xlog directory.

Changed lines from my postgresql.conf file

shared_buffers = 8192
temp_buffers = 4096
work_mem = 65536
maintenance_work_mem = 1048576
max_fsm_pages = 40000
fsync = off
wal_buffers = 64
effective_cache_size = 174848

The query above takes around 42 minutes. 

However, i also have a wimpy desktop machine with 1gb ram. Windows with
MSSQL 2000 (default installation), same database structure, same
indexes, same query, etc and it takes 17 minutes. The big difference
makes me think that i've made an error with my PostgreSQL configuration.
I just can't seem to figure it out. 

Could someone perhaps give me some pointers, advice?

Thanks in advance. 


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