Stephan Szabo <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > First thing is that you probably want to use exists instead of > in (see FAQ). Second thing is, do the two queries gather the > same rows? There are references to tables that don't seem > to be in from lists, which from lists are those tables in? > Finally, what does explain show for the two queries? Actually you should asked sql related questions on comp.databases.postgresql.sql but as for me I would look still at the explain aoutput just try and you will see for example explain select * from tabname where field>10 The output will look like : NOTICE: QUERY PLAN: Aggregate (cost=8.30..8.30 rows=1 width=4) -> Seq Scan on puantajlar (cost=0.00..7.64 rows=264 width=4) EXPLAIN It will give you an opinion about the cost of the query...and wether sequential scan or index is used.... Murat > > On Wed, 23 May 2001 [EMAIL PROTECTED] wrote: > > > Heyho, > > we tried several versions of a query which give the same results, > > but the one takes 5 secs for the first time and 0.9 secs when i > > execute the query few moments later, while the other takes ~3 secs > > always. How can this be? And how can it be that the second query > > which is in fact simpler than the first takes longer? > > > > Query 1: (5 secs vs 0.9 secs) > > > > select > > distinct > > personen_id > > from > > produktgruppen > > where > > produktgruppen.produktgruppen_id in ( > > select > > distinct > > r_gruppen_produkte.produktgruppen_id > > from > > r_gruppen_produkte > > where > > // this and the next cond are removed in 2nd query > > r_gruppen_produkte.gruppen_id = gruppen.gruppen_id > > and > > gruppen.parent_id=1 > > and > > r_gruppen_produkte.gruppen_id = r_personen_bereiche.g_id > > and > > r_personen_bereiche.p_id = 1234 > > ) > > > > Query 2: (3 secs) > > > > select > > distinct > > personen_id > > from > > produktgruppen > > where > > produktgruppen.produktgruppen_id in ( > > select > > distinct > > r_gruppen_produkte.produktgruppen_id > > from > > r_gruppen_produkte > > where > > r_gruppen_produkte.gruppen_id = r_personen_bereiche.g_id > > and > > r_personen_bereiche.p_id = 1234 > > ) > > > > Our system is Linux 2.2.16, gcc 2.95.2, Postgres 7.0.3 on a Pentium II 450, 128 megs > > > > Thanks in advance > > > > Markus Bertheau > > Cenes Data GmbH > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 6: Have you searched our list archives? > > > > http://www.postgresql.org/search.mpl > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Don't 'kill -9' the postmaster ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
