Re: patch: ALTER TABLE IF EXISTS

Hello

2012/1/2 Tomas Vondra <tv@fuzzy.cz>:
> On 2 Leden 2012, 14:11, Pavel Stehule wrote:
>> Hello
>>
>> this is relative simple patch that add possibility to skip noexisting
>> tables. It is necessary for silent cleaning when dump is loaded.
>
> Just a curious question - what use case is solved by this? Under what
> circumstances you get an ALTER TABLE without a preceding CREATE TABLE? I
> can't think of such scenario ...
>
> Or is this meant for scripts written manually so that it's possible to do
> alter if the table already exists and create if it does not exist?

this is necessary for "silent" cleaning in pg_dump

this is fragment of dump with -c option

ALTER TABLE ONLY public.b DROP CONSTRAINT b_b_fkey;
DROP INDEX public.a_a_idx;
ALTER TABLE ONLY public.a DROP CONSTRAINT a_pkey;
DROP TABLE public.b;
DROP TABLE public.a;
DROP EXTENSION plpgsql;
DROP SCHEMA public;

I am working on "silent cleaning" and I am able generate a sequence of
statements:

ALTER TABLE IF EXISTS ONLY public.b DROP CONSTRAINT b_b_fkey;
DROP INDEX IF EXISTS public.a_a_idx;
ALTER TABLE IF EXISTS ONLY public.a DROP CONSTRAINT a_pkey;
DROP TABLE IF EXISTS public.b;
DROP TABLE IF EXISTS public.a;
DROP EXTENSION IF EXISTS plpgsql;
DROP SCHEMA IF EXISTS public;

constraint  b_b_fkey should be removed before dropping index a_a_idx

Now we have DROP .. IF EXISTS statements, but  ALTER TABLE .. IF EXISTS missing

Regards

Pavel
>
> Tomas
>