Hi, On 22.1.2015 17:46, Laurent Cathala wrote: > Hi, > I'm trying to create datas on an initial import and i'm encountering a > performance issue. > I've 2 tables, my process create a record in each table and execute a > sum with join on this 2 tables. (and other requests but there are very fast) > > My 2 tables are empty before the import. > > My count query is : > select sum(quantitest0_.quantite_valeur) as col_0_0_ from > dm5_quantitestock quantitest0_, dm5_caracteristiquearticlestock > caracteris1_ where > quantitest0_.id_caracteristiquearticlestock=caracteris1_.id and > caracteris1_.id_article='4028804c4a311178014a346546967c59' > > i use parameterized request. > > My process create only 6000 records in each table. > > During the whole process this sum request lasts longer and longer. > > The auto-explain plan show an seq scan > > ---------- > Query Text: select sum(quantitest0_.quantite_valeur) as col_0_0_ from > dm5_quantitestock quantitest0_, dm5_caracteristiquearticlestock > caracteris1_ where > quantitest0_.id_caracteristiquearticlestock=caracteris1_.id and > caracteris1_.id_article=$1 > Aggregate (cost=2.04..2.05 rows=1 width=26) (actual > time=862.621..862.621 rows=1 loops=1) > Output: sum(quantitest0_.quantite_valeur) > -> Nested Loop (cost=0.00..2.04 rows=1 width=26) (actual > time=862.618..862.618 rows=0 loops=1) > Output: quantitest0_.quantite_valeur > Join Filter: > ((quantitest0_.id_caracteristiquearticlestock)::text = > (caracteris1_.id)::text) > Rows Removed by Join Filter: 1869 > -> Seq Scan on public.dm5_quantitestock quantitest0_ > (cost=0.00..1.01 rows=1 width=164) (actual time=0.004..0.408 rows=1869 > loops=1) > Output: quantitest0_.id, > quantitest0_.datefinvalidite, quantitest0_.quantite_valeur, > quantitest0_.id_caracteristiquearticlestock, > quantitest0_.id_caracteristiquelieustock, > quantitest0_.datecreationsysteme, quantitest0_.datemodificationsysteme, > quantitest0_.id_creeparsysteme, quantitest0_.id_modifieparsysteme > -> Seq Scan on public.dm5_caracteristiquearticlestock > caracteris1_ (cost=0.00..1.01 rows=1 width=42) (actual > time=0.456..0.456 rows=1 loops=1869) > Output: caracteris1_.id, > caracteris1_.datefinvalidite, caracteris1_.id_lot, > caracteris1_.id_article, caracteris1_.id_numeroserie, > caracteris1_.datecreationsysteme, caracteris1_.datemodificationsysteme, > caracteris1_.id_modifieparsysteme, caracteris1_.id_creeparsysteme > Filter: ((caracteris1_.id_article)::text = ($1)::text) > Rows Removed by Filter: 1869 > ----------- > > if a launch an analyse during the process, the explain use index, but > the time remains the same. > > --------- > Query Text: select sum(quantitest0_.quantite_valeur) as col_0_0_ from > dm5_quantitestock quantitest0_, dm5_caracteristiquearticlestock > caracteris1_ where > quantitest0_.id_caracteristiquearticlestock=caracteris1_.id and > caracteris1_.id_article=$1 > Aggregate (cost=16.55..16.56 rows=1 width=26) (actual > time=654.998..654.998 rows=1 loops=1) > Output: sum(quantitest0_.quantite_valeur) > -> Nested Loop (cost=0.00..16.55 rows=1 width=26) (actual > time=654.994..654.994 rows=0 loops=1) > Output: quantitest0_.quantite_valeur > Join Filter: ((quantitest0_.id_caracteristiquearticlestock)::text > = (caracteris1_.id)::text) > Rows Removed by Join Filter: 1651 > -> Index Scan using x_dm5_quantitestock_00 on > public.dm5_quantitestock quantitest0_ (cost=0.00..8.27 rows=1 > width=164) (actual time=0.011..0.579 rows=1651 loops=1) > Output: quantitest0_.id, quantitest0_.datefinvalidite, > quantitest0_.quantite_valeur, > quantitest0_.id_caracteristiquearticlestock, > quantitest0_.id_caracteristiquelieustock, > quantitest0_.datecreationsysteme, quantitest0_.datemodificationsysteme, > quantitest0_.id_creeparsysteme, quantitest0_.id_modifieparsysteme > -> Index Scan using dm5_caracteristiquearticlestock_pkey on > public.dm5_caracteristiquearticlestock caracteris1_ (cost=0.00..8.27 > rows=1 width=42) (actual time=0.395..0.395 rows=1 loops=1651) > Output: caracteris1_.id, caracteris1_.datefinvalidite, > caracteris1_.id_lot, caracteris1_.id_article, > caracteris1_.id_numeroserie, caracteris1_.datecreationsysteme, > caracteris1_.datemodificationsysteme, caracteris1_.id_modifieparsysteme, > caracteris1_.id_creeparsysteme > Filter: ((caracteris1_.id_article)::text = > '4028804c4a311178014a346547307cce'::text) > Rows Removed by Filter: 1651 > > ---------- Why is the first query using a parameter ($1) while the second one uses a string literal? Have you executed them differently? > > If i create the first 1000 records, commit and end transaction, the > whole import is very fast. And what plans do the queries use? > > I can't change my process to cut the process in little part... We're talking about a 600-800 ms query - even if you cut it to 1 ms, I don't see how this would do a difference in a batch-style job. If you're doing many such queries (with different id_article values), you may do something like this select caracteris1_.id_article, sum(quantitest0_.quantite_valeur) as col_0_0_ from dm5_quantitestock quantitest0_, dm5_caracteristiquearticlestock caracteris1_ where quantitest0_.id_caracteristiquearticlestock=caracteris1_.id group by caracteris1_.id_article and then query this (supposedly much smaller) table. regards -- Tomas Vondra http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
