[postgis-users] CPU tuning

Olivier Leprêtre o.lepretre at gmail.com
Sun Jan 8 07:36:04 PST 2017



I have a pgsql postgis function that last about an hour on an Hp Envy (W10,
i7-6500 CPU 2,5 Ghz 8go). This function is calculating minimum distance
between each nodes of table x (12000 nodes) and table y (42000 nodes)


FOR row IN 

                   SELECT code,ST_AsEwkt(ST_StartPoint(geom)) as geom1  FROM


                   FOR row1 IN

                            SELECT code,
ST_Distance(ST_AsEwkt(geom)::text,row.geom1) FROM t_y order by
ST_Distance(ST_AsEwkt(geom)::text,row.geom1) LIMIT 1



                   END LOOP;




What I don't understand is that postgresql server process CPU is stable
during all that time at 30/31% with no other process running. Details of
each processor 1 to 3 shows that all 4 uses 30%. Disk and network usage are
0% (database is local) Ram usage is 47% and Postgresql server uses process
only 7,4 Mo.


My question is "Why postgres process uses such a precise and constant cpu
and doesn't grow up to more than 30% ?" I didn't find any parameter forcing
such a limit in order to reduce duration of this calculation.


Thanks for any answer,



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