On Sun, Oct 7, 2012 at 3:49 PM, <vi...@chem.elte.hu> wrote: > Hello! > > I would like to ask following question: > I have created a table and I updated all records. > And I executed this update command again and again.... > Execution time was growing after each step. > I cannot understand this behavior. > First update command took 6 sec, 30th update (same) command took 36 sec > (6x times greater value!!!). > Can somebody explain me why increasing this update time? > > -- 1st update: 6175 ms > -- 5th update: 9265 ms > -- 10th update: 15669 ms > -- 20th update: 26940 ms > -- 20th update: 36198 ms > > PGSQL version: 9.1.5, parameters: default install used > > Thanks your answer in advance! > > SCRIPT: > > DROP SCHEMA IF EXISTS tempdb CASCADE; > CREATE SCHEMA tempdb; > SET search_path TO tempdb; > > DROP TABLE IF EXISTS t; > CREATE TABLE t ( > id SERIAL , > num int NOT NULL, > PRIMARY KEY (id) > ); > > > insert into t > SELECT *,0 FROM generate_series(1,100000); > > update t set num=num+1; -- 1st update: 6175 ms > update t set num=num+1; > update t set num=num+1; >
Hello, could you do the same putting VACUUM t; between your updates? What is the change in UPDATE time? -- Valentin
