Re: 57 minute SELECT

Total RAM = 1G is correct

This query executes as the result of a search from our Network Management System Device Audit web tool where the date
rangeis large and is focused on a specific device. 

I was thinking it should execute more quickly since syslog.ip has an index and we're not performing any textual
matching.

EXPLAIN:

QUERY PLAN

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Hash Join  (cost=408.53..1962721.39 rows=98068 width=126) (actual time=30121.265..3419306.752 rows=1929714 loops=1)
   Hash Cond: (public.syslog_master.ip = public.devices.ip)
   ->  Nested Loop  (cost=209.67..1120466.90 rows=37316116 width=122) (actual time=30117.845..3416690.561 rows=1929714
loops=1)
         Join Filter: (public.syslog_master.ip = public.devices.ip)
         ->  HashAggregate  (cost=205.40..205.41 rows=1 width=7) (actual time=5.133..5.142 rows=1 loops=1)
               ->  Nested Loop  (cost=0.00..205.40 rows=1 width=7) (actual time=4.117..5.124 rows=1 loops=1)
                     Join Filter: ((public.devices.hostgroup)::text = (mongroups.hostgroup)::text)
                     ->  Seq Scan on devices  (cost=0.00..202.80 rows=1 width=14) (actual time=4.088..5.075 rows=1
loops=1)
                           Filter: ((id <> 1291) AND ((active = 't'::bpchar) OR (active = 's'::bpchar)) AND
((((hostname)::text|| '.'::text) || (hostpop)::text) ~* 'pe1.mel4'::text)) 
                     ->  Seq Scan on mongroups  (cost=0.00..1.71 rows=71 width=6) (actual time=0.009..0.017 rows=71
loops=1)
         ->  Append  (cost=4.27..1114378.69 rows=470624 width=115) (actual time=30112.646..3415201.052 rows=1929766
loops=1)
               ->  Bitmap Heap Scan on syslog_master  (cost=4.27..9.61 rows=2 width=72) (actual time=0.027..0.027
rows=0loops=1) 
                     Recheck Cond: (public.syslog_master.ip = public.devices.ip)
                     Filter: ((public.syslog_master.datetime <= '2013-08-01 00:00:00'::timestamp without time zone) AND
(public.syslog_master.datetime>= '2013-04-12 00:00:00'::timestamp without time zone)) 
                     ->  Bitmap Index Scan on syslog_master_ip_idx  (cost=0.00..4.27 rows=2 width=0) (actual
time=0.019..0.019rows=0 loops=1) 
                           Index Cond: (public.syslog_master.ip = public.devices.ip)
               ->  Bitmap Heap Scan on syslog_201307 syslog_master  (cost=4175.37..355209.50 rows=150004 width=112)
(actualtime=30112.618..686289.128 rows=297015 loops=1) 
                     Recheck Cond: (public.syslog_master.ip = public.devices.ip)
                     Filter: ((public.syslog_master.datetime <= '2013-08-01 00:00:00'::timestamp without time zone) AND
(public.syslog_master.datetime>= '2013-04-12 00:00:00'::timestamp without time 

-----Original Message-----
From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of David
Johnston
Sent: Thursday, 3 October 2013 10:47 AM
To: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] 57 minute SELECT

Samuel Stearns-2 wrote
> Total RAM - 1G
>
>
> 1.       Explain on SELECT.

So either this is a typo (1 GB of RAM) or your query is likely ending up I/O bound.

You should probably provide EXPLAIN and EXPLAIN (ANALYZE) output since even with the schema it is impossible for
someoneto see what the planner is proposing for a multiple-million record source table that is going to be empty if all
someonedoes is create the schema. 

For my money it is also helpful to actual write some prose describing what you are providing and seeing and not just
tosssome settings and schema out there. 

http://wiki.postgresql.org/wiki/SlowQueryQuestions

David J.




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