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Re: Show <parameter> in psql does any calculations?

From: Raghavendra <raghavendra(dot)rao(at)enterprisedb(dot)com>
To: Filip Rembiałkowski <plk(dot)zuber(at)gmail(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Show <parameter> in psql does any calculations?
Date: 2011-12-28 05:27:25
Message-ID: CA+h6AhitM=KS0ieYb8ZbdKfj9W-cLX68=nc6xffLV+Xzh+enpg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-general
Thanks all for clarifying me... Good to know this...

---
Regards,
Raghavendra
EnterpriseDB Corporation
Blog: http://raghavt.blogspot.com/



2011/12/27 Filip Rembiałkowski <plk(dot)zuber(at)gmail(dot)com>

> so as long as actual logic is buried in the guts of psql, best you can
> do in SQL to get human-readable value is
>
> SELECT name, setting, unit, case when unit='kB' then
> pg_size_pretty(setting::int*1024) when unit='8kB' then
> pg_size_pretty(setting::int*1024*8) else coalesce(setting||'
> '||unit,setting) end AS setting_human_readable,
> context FROM pg_settings WHERE category like '%Resource Usage /
> Memory%' ORDER BY name;
>
>
> Filip
>
>
> 2011/12/27 Raghavendra <raghavendra(dot)rao(at)enterprisedb(dot)com>:
> >
> > On Tue, Dec 27, 2011 at 3:16 PM, Guillaume Lelarge <
> guillaume(at)lelarge(dot)info>
> > wrote:
> >>
> >> On Tue, 2011-12-27 at 14:56 +0530, Raghavendra wrote:
> >> > Respected,
> >> >
> >> > Am in PG 9.1. See below ouputs.
> >> >
> >> > *By query:*
> >> > postgres=# SELECT name, setting, unit,context FROM pg_settings WHERE
> >> > category like '%Resource Usage / Memory%' ORDER BY name;
> >> >            name            | setting | unit |  context
> >> > ---------------------------+---------+------+------------
> >> >  maintenance_work_mem      | 16384   | kB   | user
> >> >  max_prepared_transactions  | 0          |       | postmaster
> >> >  max_stack_depth                 | 2048    | kB   | superuser
> >> >  shared_buffers                     | 4096    | 8kB  | postmaster
> >> >  temp_buffers                       | 1024    | 8kB  | user
> >> >  track_activity_query_size     | 1024    |      | postmaster
> >> >  work_mem                          | 2048    | kB   | user
> >> > (7 rows)
> >> >
> >> > *By session command:*
> >> > postgres=# show work_mem ;
> >> >  work_mem
> >> > ----------
> >> >  2MB
> >> > (1 row)
> >> >
> >> > postgres=# show shared_buffers ;
> >> >  shared_buffers
> >> > ----------------
> >> >  32MB
> >> > (1 row)
> >> >
> >> > By the query, its clear that "setting" value is multiplied with unit
> to
> >> > get
> >> > the sesssion level command value which is displayed here. However, I
> am
> >> > trying to get the query of it which is executed at session-level with
> >> > SHOW
> >> > command. I tried "psql -E" option tooo..
> >> >
> >> > -bash-3.2$ psql -E
> >> > psql.bin (9.1.0)
> >> > Type "help" for help.
> >> >
> >> > postgres=# show work_mem ;
> >> >  work_mem
> >> > ----------
> >> >  2MB
> >> > (1 row)
> >> >
> >> > Why the query is not displayed with -E option ?
> >> > Am I missing something here, please help me in clarifying it.
> >> >
> >>
> >> -E works only for meta-commands, ie commands which start with \
> >>
> >> Moreover, SHOW is an actual SQL command. So I'm not sure what you're
> >> trying to find with the -E command line switch.
> >>
> >
> > Hey, Many thanks for your quick response.
> >
> > I am looking how SHOW command value is converted into MB's or GB's ?
> >
> > ---
> > Regards,
> > Raghavendra
> > EnterpriseDB Corporation
> > Blog: http://raghavt.blogspot.com/
> >
>

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