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Re: Truncate if exists

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Truncate if exists
Date: 2012-10-12 19:04:56
Message-ID: CA+TgmobQ8dpgRObHXh1mp=B3b5L-nJrWz=8oSttvNZXGOkK=Ag@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, Oct 11, 2012 at 3:22 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> So we just need a function called pg_if_table_exists(table, SQL) which
> wraps a test in a subtransaction.
>
> And you write
>
> SELECT pg_if_table_exists('foo', 'TRUNCATE TABLE foo');
>
> and we can even get rid of all that other DDL crud that's been added....
>
> and we can have pg_if_table_not_exists() also.

You could make this more composable by having pg_table_exists() and
pg_execute_sql_from_string().  Then you can write: SELECT CASE WHEN
pg_table_exists(...) THEN pg_execute_sql_from_string(...) END.  And if
you want the if-not-exists case then just stick a NOT in there.  And
if you want a more complicated condition, you can easily write that as
well.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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