2010/11/21 Humair Mohammed <humairm@xxxxxxxxxxx>: > > 1) OS/Configuration > 64-bit Windows 7 Enterprise with 8G RAM and aÂDual Core 2.67 Ghz Intel CPU > postgresql-x64-9.0 (PostgreSQL 9.0.1, compiled by Visual C++ build 1500, > 64-bit) > work_mem Â2GB > 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)ÂEXPLAIN (ANALYZE ON, BUFFERS ON) > "Hash Join Â(cost=16212.30..52586.43 rows=92869 width=17) (actual > time=25814.222..32296.765 rows=3163 loops=1)" > " ÂHash Cond: (((pb.id)::text = (pg.id)::text) AND ((pb.question)::text = > (pg.question)::text))" > " ÂJoin Filter: ((COALESCE(pb.response, 'MISSING'::character varying))::text > <> (COALESCE(pg.response, 'MISSING'::character varying))::text)" > " ÂBuffers: shared hit=384 read=6511, temp read=6444 written=6318" > " Â-> ÂSeq Scan on pivotbad pb Â(cost=0.00..2804.96 rows=93496 width=134) > (actual time=0.069..37.143 rows=93496 loops=1)" > " Â Â Â ÂBuffers: shared hit=192 read=1678" > " Â-> ÂHash Â(cost=7537.12..7537.12 rows=251212 width=134) (actual > time=24621.752..24621.752 rows=251212 loops=1)" > " Â Â Â ÂBuckets: 1024 ÂBatches: 64 ÂMemory Usage: 650kB" > " Â Â Â ÂBuffers: shared hit=192 read=4833, temp written=4524" > " Â Â Â Â-> ÂSeq Scan on pivotgood pg Â(cost=0.00..7537.12 rows=251212 > width=134) (actual time=0.038..117.780 rows=251212 loops=1)" > " Â Â Â Â Â Â ÂBuffers: 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. > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
