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That was a typo: work_mem = 2GB shared_buffers = 2GB > From: pavel.stehule@xxxxxxxxx > Date: Sun, 21 Nov 2010 12:38:43 +0100 > Subject: Re: Query Performance SQL Server vs. Postgresql > To: humairm@xxxxxxxxxxx > CC: pgsql-performance@xxxxxxxxxxxxxx > > 2010/11/21 Humair Mohammed <humairm@xxxxxxxxxxx>: > > > > 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. > > |
