Re: See Temp Table from Trigger
От | Christoph Haller |
---|---|
Тема | Re: See Temp Table from Trigger |
Дата | |
Msg-id | 3EC4A444.75A2DD8B@rodos.fzk.de обсуждение исходный текст |
Ответ на | See Temp Table from Trigger ("Joachim Zauner" <j.zauner@epcom.cc>) |
Список | pgsql-sql |
> > Hi List! > Is there a way a Trigger can see a Temporary Table or better - check if a > Temp Table exists? > - Or can i define a "Session Variable" that will allow this? Joachim, Find below a previuos thread on temp-table-existence. Hope this helps. Regards, Christoph From: Mike Papper <m.papper@fantastic.com> Subject: [SQL] Finding if a temp table exists in the current connection Date: Wed, 02 Apr 2003 00:09:33 -0800 Is there a way (i.e., access theinternal pg_ tables) to find out if a particular temp table already exists (in the current connection)? I have written some stored procedures that check if a table exists and if a column exists in a table. This is used so I can perform upgrades of our system (if table doesnt exist, call create table... sql). I would like to do a similar thing for temp tables. I have noticed that if another connection creates a temp table, it will show up in the pg_* tables so that all ocnnections can see the table. Is there some standard SQL way to test? -- Mike Papper From: Christoph Haller <ch@rodos.fzk.de> Subject: Re: [SQL] Finding if a temp table exists in the current connection Date: Fri, 04 Apr 2003 13:16:16 +0200 >> Is there a way (i.e., access theinternal pg_ tables) to find out if a > particular temp table already exists (in the current connection)?>> I have written some stored procedures that check ifa table exists and if a> column exists in a table. This is used so I can perform upgrades of our> system (if table doesnt exist, call create table... sql).>> I would like to do a similar thing for temp tables.>> Ihave noticed that if another connection creates a temp table, it will> show up in the pg_* tables so that all ocnnections can see the table. >> Is there some standard SQL way to test?> I'm using 7.3.2 and it seems there is a way. I've found out by starting a psql session using the -E option. This shows you the SQL behind \dt which shows the current temp tables. It looks like they are created in name spaces called "pg_temp_<N>, where N is simply a connection counter. SELECT n.nspname as "Schema",c.relname as "Name" FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace where n.nspname like 'pg_temp_%' AND pg_catalog.pg_table_is_visible(c.oid) ; If I do (within 1st connection) create temp table tgif (dummy int); and the select above returns Schema | Name -----------+------pg_temp_1 | tgif (1 row) And within a 2nd connection create temp table tgif (dummy int); and the select above returns Schema | Name -----------+------pg_temp_2 | tgif (1 row) Does this help? Regards, Christoph From: Tom Lane <tgl@sss.pgh.pa.us> Subject: Re: [SQL] Finding if a temp table exists in the current connection Date: Fri, 04 Apr 2003 09:58:24 -0500 Christoph Haller <ch@rodos.fzk.de> writes: > It looks like they are created in name spaces called "pg_temp_<N>, > where N is simply a connection counter. Right. If you are trying to find out which N applies to your session, here is one way: regression=# select current_schemas(true); current_schemas ---------------------{pg_catalog,public} (1 row) regression=# create temp table z(f1 int); CREATE TABLE regression=# select current_schemas(true); current_schemas -------------------------------{pg_temp_2,pg_catalog,public} (1 row) regards, tom lane
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