That was a typo:
work_mem = 2GBshared_buffers = 2GB
> From: pavel(dot)stehule(at)gmail(dot)com
> Date: Sun, 21 Nov 2010 12:38:43 +0100
> Subject: Re: [PERFORM] Query Performance SQL Server vs. Postgresql
> To: humairm(at)hotmail(dot)com
> CC: pgsql-performance(at)postgresql(dot)org
>
> 2010/11/21 Humair Mohammed <humairm(at)hotmail(dot)com>:
> >
> > 1) OS/Configuration
> > 64-bit Windows 7 Enterprise with 8G RAM and a Dual Core 2.67 Ghz Intel CPU
> > postgresql-x64-9.0 (PostgreSQL 9.0.1, compiled by Visual C++ build 1500,
> > 64-bit)
> > work_mem 2GB
> > shared_buffers = 2
>
> shared_buffers = 2 ???
>
> Regards
>
> Pavel Stehule
>
>
> > 2) Dataset
> > name,pages,tuples,pg_size_pretty
> > "pivotbad";1870;93496;"15 MB"
> > "pivotgood";5025;251212;"39 MB"
> > 3) EXPLAIN (ANALYZE ON, BUFFERS ON)
> > "Hash Join (cost=16212.30..52586.43 rows=92869 width=17) (actual
> > time=25814.222..32296.765 rows=3163 loops=1)"
> > " Hash Cond: (((pb.id)::text = (pg.id)::text) AND ((pb.question)::text =
> > (pg.question)::text))"
> > " Join Filter: ((COALESCE(pb.response, 'MISSING'::character varying))::text
> > <> (COALESCE(pg.response, 'MISSING'::character varying))::text)"
> > " Buffers: shared hit=384 read=6511, temp read=6444 written=6318"
> > " -> Seq Scan on pivotbad pb (cost=0.00..2804.96 rows=93496 width=134)
> > (actual time=0.069..37.143 rows=93496 loops=1)"
> > " Buffers: shared hit=192 read=1678"
> > " -> Hash (cost=7537.12..7537.12 rows=251212 width=134) (actual
> > time=24621.752..24621.752 rows=251212 loops=1)"
> > " Buckets: 1024 Batches: 64 Memory Usage: 650kB"
> > " Buffers: shared hit=192 read=4833, temp written=4524"
> > " -> Seq Scan on pivotgood pg (cost=0.00..7537.12 rows=251212
> > width=134) (actual time=0.038..117.780 rows=251212 loops=1)"
> > " Buffers: shared hit=192 read=4833"
> > "Total runtime: 32297.305 ms"
> > 4) INDEXES
> > I can certainly add an index but given the table sizes I am not sure if that
> > is a factor. This by no means is a large dataset less than 350,000 rows in
> > total and 3 columns. Also this was just a quick dump of data for comparison
> > purpose. When I saw the poor performance on the COALESCE, I pointed the data
> > load to SQL Server and ran the same query except with the TSQL specific
> > ISNULL function.
> >