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From: tv@fuzzy.cz
To: Humair Mohammed <humairm@hotmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Query Performance SQL Server vs. Postgresql
Date: Sun, 21 Nov 2010 16:42:07 +0100
Message-ID: <1cc426dab35a9fc3fd189d5f9a6fb7a0.squirrel@sq.gransy.com> (raw)
In-Reply-To: <ef40ef98515c88b82f63c7d6cc421f12.squirrel@sq.gransy.com>
References: <COL115-W5250BF8BDC50E0A64DABE4A8360@phx.gbl>
	<AANLkTin+MPhrYUzkCZjdAMLhF3KKZCCuvDm0=Npf9jz7@mail.gmail.com>
	<COL115-W3987D9D7DE908C5C47792DA8380@phx.gbl>
	<AANLkTi=yFV69yNZpHzKiZRtZ0X0PtKcpOrMNNkAo+Si6@mail.gmail.com>
	<COL115-W186A7B93051E6907958ED6A8380@phx.gbl>
	<AANLkTinQmaQ5Ui-vQwfqWFtOTCj76NWFBr6VDKMdVUCs@mail.gmail.com>
	<COL115-W5263E5369E2BD0B28E78B9A83C0@phx.gbl>
	<ef40ef98515c88b82f63c7d6cc421f12.squirrel@sq.gransy.com>

>> 4) INDEXESI 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.
>
> 350000 rows definitely is a lot of rows, although with 3 INT column it's
> just about 13MB of data (including overhead). But indexes can be quite
> handy when doing joins, as in this case.

OK, I've just realized the tables have 3 character columns, not integers.
In that case the tables are probably much bigger (and there are things
like TOAST). In that case indexes may be even more important.

Tomas




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  Cc: tv@fuzzy.cz, humairm@hotmail.com
  Subject: Re: Query Performance SQL Server vs. Postgresql
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