Re: BUG #7571: Query high memory usage - Mailing list pgsql-bugs

Hi Pavel,

Here are the test data with set enable_hashagg to off. It does not looks
like improvement. Query was running for 30min without returning result set.

db=> set enable_hashagg=off;
SET
db=> explain
db-> SELECT
db->   schema_name,
db->   sum(table_size)
db-> FROM
db->   (SELECT
db(>     pg_catalog.pg_namespace.nspname as schema_name,
db(>     pg_relation_size(pg_catalog.pg_class.oid) as table_size,
db(>     sum(pg_relation_size(pg_catalog.pg_class.oid)) over () as
database_size
db(>    FROM pg_catalog.pg_class
db(>    JOIN pg_catalog.pg_namespace
db(>     ON relnamespace = pg_catalog.pg_namespace.oid
db(>   ) t
db-> GROUP BY schema_name, database_size;
                                                    QUERY PLAN
------------------------------------------------------------------------------------------------------------------
 GroupAggregate  (cost=725540.59..756658.18 rows=40000 width=104)
   ->  Sort  (cost=725540.59..733219.99 rows=3071759 width=104)
         Sort Key: pg_namespace.nspname,
(sum(pg_relation_size((pg_class.oid)::regclass, 'main'::text)) OVER (?))
         ->  WindowAgg  (cost=120.98..243838.73 rows=3071759 width=68)
               ->  Hash Join  (cost=120.98..190082.95 rows=3071759 width=68)
                     Hash Cond: (pg_class.relnamespace = pg_namespace.oid)
                     ->  Seq Scan on pg_class  (cost=0.00..143885.59
rows=3071759 width=8)
                     ->  Hash  (cost=90.99..90.99 rows=2399 width=68)
                           ->  Seq Scan on pg_namespace  (cost=0.00..90.99
rows=2399 width=68)
(9 rows)


Data from top after 30 min of query run with hashagg set off:
  PID  USER     PR  NI  VIRT   RES  SHR S %CPU %MEM    TIME+    COMMAND
 2235 postgres  25   0   27.5g  23g    4.6g R  95.1    75.2        31:39.81
postgres: aspuser aspdata 10.0.2.67(52716) SELECT


Radovan

On Wed, Sep 26, 2012 at 10:15 PM, Pavel Stehule <pavel.stehule@gmail.com>wrote:

> Hello
>
> you should to run this query on real data - and if it works now, then
> send EXPLAIN ANALYZE result, please
>
> Pavel
>
> 2012/9/27 Melese Tesfaye <mtesfaye@gmail.com>:
> > Thanks Pavel,
> > Setting enable_hashagg to off didn't resolve the issue.
> > Please find the explain as well as query results after "set
> > enable_hashagg=off;"
> >
> > mtesfaye@[local](test_db)=# EXPLAIN SELECT DISTINCT(A.*)
> > test_db-# FROM table1_t A LEFT JOIN table2_v B
> > test_db-# ON A.pnr_id=B.pnr_id
> > test_db-# WHERE  A.pnr_id IN(1801,2056) AND
> > B.departure_date_time>=DATE('2012-09-26')
> > test_db-# ORDER BY pnr_id ASC,nam_id ASC;
> >
> +-----------------------------------------------------------------------------------------------------------+
> > |                                                QUERY PLAN
> > |
> >
> +-----------------------------------------------------------------------------------------------------------+
> > | Unique  (cost=1354.62..1354.66 rows=4 width=13)
> > |
> > |   ->  Sort  (cost=1354.62..1354.63 rows=4 width=13)
> > |
> > |         Sort Key: a.pnr_id, a.nam_id, a.pty_num
> > |
> > |         ->  Merge Join  (cost=1084.06..1354.58 rows=4 width=13)
> > |
> > |               Merge Cond: (table2_t.pnr_id = a.pnr_id)
> > |
> > |               ->  Unique  (cost=1084.06..1198.67 rows=11461 width=16)
> > |
> > |                     ->  Sort  (cost=1084.06..1112.72 rows=11461
> width=16)
> > |
> > |                           Sort Key: table2_t.pnr_id, table2_t.itn_id,
> > table2_t.departure_date_time        |
> > |                           ->  Seq Scan on table2_t  (cost=0.00..311.34
> > rows=11461 width=16)               |
> > |                                 Filter: (departure_date_time >=
> > '2012-09-26'::date)                       |
> > |               ->  Index Scan using table1_t_pnr_id_idx1 on table1_t a
> > (cost=0.00..12.60 rows=4 width=13) |
> > |                     Index Cond: (pnr_id = ANY
> ('{1801,2056}'::integer[]))
> > |
> >
> +-----------------------------------------------------------------------------------------------------------+
> > (12 rows)
> >
> > Time: 5.889 ms
> >
> > mtesfaye@[local](test_db)=# show enable_hashagg;
> > +----------------+
> > | enable_hashagg |
> > +----------------+
> > | on             |
> > +----------------+
> > (1 row)
> >
> > Time: 0.136 ms
> >
> > mtesfaye@[local](test_db)=# set enable_hashagg=off;
> > SET
> > Time: 0.203 ms
> > mtesfaye@[local](test_db)=# show enable_hashagg;
> > +----------------+
> > | enable_hashagg |
> > +----------------+
> > | off            |
> > +----------------+
> > (1 row)
> >
> > Time: 0.131 ms
> >
> >
> > mtesfaye@[local](test_db)=# SELECT DISTINCT(A.*)
> > test_db-# FROM table1_t A LEFT JOIN table2_v B
> > test_db-# ON A.pnr_id=B.pnr_id
> > test_db-# WHERE  A.pnr_id IN(1801,2056) AND
> > B.departure_date_time>=DATE('2012-09-26')
> > test_db-# ORDER BY pnr_id ASC,nam_id ASC;
> > +--------+--------+---------+
> > | pnr_id | nam_id | pty_num |
> > +--------+--------+---------+
> > |   1801 |   3359 |       1 |
> > |   1801 |   3360 |       1 |
> > |   1801 |   3361 |       1 |
> > |   1801 |   3362 |       1 |
> > +--------+--------+---------+
> > (4 rows)
> >
> > Time: 8.452 ms
> >
> >
> > On Thu, Sep 27, 2012 at 3:54 AM, Pavel Stehule <pavel.stehule@gmail.com>
> > wrote:
> >>
> >> Hello
> >>
> >> this situation is possible, when optimizer use HashAgg where should not
> >> use it.
> >>
> >> Please, try to disable HashAgg - set enable_hashagg to off;
> >>
> >> please, send EXPLAIN result
> >>
> >> Regards
> >>
> >> Pavel Stehule
> >>
> >> 2012/9/26  <radovan.jablonovsky@replicon.com>:
> >> > The following bug has been logged on the website:
> >> >
> >> > Bug reference:      7571
> >> > Logged by:          Radovan Jablonovsky
> >> > Email address:      radovan.jablonovsky@replicon.com
> >> > PostgreSQL version: 9.1.5
> >> > Operating system:   CentOs 5.8 Linux 2.6.18-308.el5 x86_64
> >> > Description:
> >> >
> >> > During checking our company database size we used query, which was not
> >> > the
> >> > best to find out the tables/db size but should do the job. The query
> was
> >> > tested on server with 32GB of RAM, 2 CPU with 4 cores and it was
> running
> >> > alone without other activity. It consumed almost all RAM forced server
> >> > to
> >> > use swap and after 1hour it was still running. The simplified version
> of
> >> > query used 20% of memory and finished after 1hour 8min.
> >> >
> >> > The size of pg_class is 3mil rows/objects and pg_namespace has 3000
> >> > rows/schemata.
> >> >
> >> > query:
> >> > SELECT
> >> >   schema_name,
> >> >   sum(table_size)
> >> > FROM
> >> >   (SELECT
> >> >     pg_catalog.pg_namespace.nspname as schema_name,
> >> >     pg_relation_size(pg_catalog.pg_class.oid) as table_size,
> >> >     sum(pg_relation_size(pg_catalog.pg_class.oid)) over () as
> >> > database_size
> >> >    FROM pg_catalog.pg_class
> >> >    JOIN pg_catalog.pg_namespace
> >> >     ON relnamespace = pg_catalog.pg_namespace.oid
> >> >   ) t
> >> > GROUP BY schema_name, database_size;
> >> >
> >> >
> >> > top - 10:50:44 up 20 days, 19:00,  1 user,  load average: 1.15, 1.10,
> >> > 0.84
> >> > Tasks: 239 total,   3 running, 236 sleeping,   0 stopped,   0 zombie
> >> > Cpu(s): 15.1%us,  1.5%sy,  0.0%ni, 83.0%id,  0.5%wa,  0.0%hi,  0.0%si,
> >> > 0.0%st
> >> > Mem:  32946260k total, 32599908k used,   346352k free,   141924k
> buffers
> >> > Swap: 55043952k total,    85216k used, 54958736k free, 14036516k
> cached
> >> >
> >> > Info from top:
> >> >   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> >> >  2016 postgres  25   0 22.8g  17g 3.2g R 96.1 56.0  19:17.01 postgres:
> >> > postgres db 10.0.1.10(49928) SELECT
> >> >
> >> > Simplified version of query uses pg_tables. It has 0.5mil rows/tables.
> >> > Simplified version of query:
> >> > SELECT
> >> >   schemaname,
> >> >   sum(pg_relation_size(schemaname || '.' || tablename))::bigint
> >> > FROM pg_tables
> >> > GROUP BY schemaname;
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org)
> >> > To make changes to your subscription:
> >> > http://www.postgresql.org/mailpref/pgsql-bugs
> >>
> >>
> >> --
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> >
> >
>