<p><font size="2">Tom,</font><p><font size="2">Thanks for your answer. The problem is indeed related to the
statistics.</font><br/><font size="2">The isssue now seems to find out why the statistics are 'incorrect' every
day.</font><br/><font size="2">My gues is the following: we run every night the command VACUUM ANALYZE. This command
returnwrong statistics info. Because when I run ANALYZE only on a table, everything is fine.</font><p><font size="2">We
areon PosgreSQL 7.4.</font><br /><p><font size="2">Groet,</font><br /><font size="2">Fred Vellinga</font><br /><br
/><p><fontsize="2">-----Original Message-----</font><br /><font size="2">From: Tom Lane [<a
href="mailto:tgl@sss.pgh.pa.us">mailto:tgl@sss.pgh.pa.us</a>]</font><br /><font size="2">Sent: 11 April 2006
04:58</font><br/><font size="2">To: Vellinga, Fred</font><br /><font size="2">Cc: 'pgsql-sql@postgresql.org'</font><br
/><fontsize="2">Subject: Re: [SQL] Special meaning of NL string </font><br /><p><font size="2">"Vellinga, Fred"
<fred.vellinga@nl.verizonbusiness.com>writes:</font><br /><font size="2">> The query</font><br /><font
size="2">>SELECT COUNT(*) FROM Table WHERE Field1 = 'NL' OR Field2 = 'NL' does a </font><br /><font size="2">>
sequencescan instead of an index scan, and is thus very slow. If I </font><br /><font size="2">> replace NL by BE
(Belgium)the query does an index scan.</font><p><font size="2">Probably, 'NL' is a lot more common than 'BE' in your
table... the planner does examine statistics while deciding what sort of scan to use.</font><p>
<fontsize="2">regards, tom lane</font>
