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query slows down drastically with increased number of fields - Mailing list pgsql-performance

From Tom Darci
Subject query slows down drastically with increased number of fields
Date
Msg-id 6FB011BE26AACD4CB5F2B505AE0BEB2E020B6E86@MI8NYCMAIL05.Mi8.com
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Responses Re: query slows down drastically with increased number of fields
Re: query slows down drastically with increased number of fields
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Hello All-
 
  We have a question about numbers of fields in the select clause of a query and how that affects query speed.
  The following query simply selects the primary key field from a table with 100,000 records:
 
------------------------------------------------------------
select p.opid
FROM
ott_op p
------------------------------------------------------------
 
  It runs in about half a second (running in PgAdmin... the query run time, not the data retrieval time)
 
  When we change it by adding fields to the select list, it slows down drastically. This version takes about 3 seconds:
 
------------------------------------------------------------
select p.opid, p.opid, p.opid, p.opid, p.opid, p.opid, p.opid, p.opid, p.opid, p.opid, p.opid
FROM
ott_op p
------------------------------------------------------------
 
  The more fields we add, the slower it gets.
 
  My guess is that we are missing a configuration setting... any ideas?
  Any help much appreciated.
 
Thanks,
-Tom

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