PostgreSQL SQL - DROP TYPE without error?

Author

DROP TYPE without error?

Philippe Lang

2005-04-06, 8:03 pm

Hi,

Since it is not possible to use CREATE OR REPLACE TYPE, is there a way
of using DROP TYPE on a non-existing type, without causing the entire
script to abort? It may sound crazy to ask for this, but it could be
really useful in my case, where Pl/Pgsql and Pl/Perl code is being
generated automatically, based on data found in a database.

Thanks

-----------------
Philippe Lang

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Mischa

2005-04-06, 8:03 pm

Quoting Philippe Lang <philippe.lang@attiksystem.ch>:

> Since it is not possible to use CREATE OR REPLACE TYPE, is there a way
> of using DROP TYPE on a non-existing type, without causing the entire
> script to abort? It may sound crazy to ask for this, but it could be
> really useful in my case, where Pl/Pgsql and Pl/Perl code is being
> generated automatically, based on data found in a database.

I've got a similar request for other objects that do/do not exist.
Maybe it's just that I got lazy using MSSQL, but it sure was convenient
to have:

IF object_id('WorkTable
') IS NULL
CREATE TABLE WorkTable(...
etc.

Given that you cannot just execute an anonymous block of PL/PGSQL code,
where you could do the test AND the create ...

--
"Dreams come true, not free."

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Harald Fuchs

2005-04-07, 8:03 pm

In article <1112817807. 4254408fecadc@webmai
l.telus.net>,
Mischa <mischa.Sandberg@telus.net> writes:

> I've got a similar request for other objects that do/do not exist.
> Maybe it's just that I got lazy using MSSQL, but it sure was convenient
> to have:

> IF object_id('WorkTable
') IS NULL
> CREATE TABLE WorkTable(...
> etc.

I got lazy using MySQL, where it was convenient to have
CREATE TABLE IF NOT EXISTS tbl (...)
and
DROP TABLE IF EXISTS tbl

This is the only feature of MySQL I really miss.

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Jeff Boes

2005-04-07, 8:03 pm

Philippe Lang wrote:
> Hi,
>
> Since it is not possible to use CREATE OR REPLACE TYPE, is there a way
> of using DROP TYPE on a non-existing type, without causing the entire
> script to abort? It may sound crazy to ask for this, but it could be
> really useful in my case, where Pl/Pgsql and Pl/Perl code is being
> generated automatically, based on data found in a database.
>

If I understand you correctly, then this might be useful:

begin;
select now();

\o tmp.tmp
\qecho 'drop type \"foofookitty\";'
\o
\! psql -f tmp.tmp

select now();
commit;

--
Jeff Boes Vox 269-226-9550 x24
Director of Software Development Fax 269-349-9076

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Craig Addleman

2005-04-10, 8:24 pm

I was confronted with a similar problem. I have several scripts which create
or modify schemas, and each run in a single transaction. So, dropping a
non-existent TYPE will produce a show-stopping error. I wrote this function,
and others for various database objects:

CREATE OR REPLACE FUNCTION dba_droptype(varchar
) RETURNS boolean AS '
DECLARE
p_type ALIAS FOR $1;
v_exists boolean;
BEGIN
SELECT INTO v_exists TRUE WHERE EXISTS(
SELECT 1 FROM pg_type
WHERE typname = p_type::name);
IF v_exists THEN
RAISE NOTICE ''Dropping TYPE %'', p_type;
EXECUTE ''DROP TYPE '' || p_type || '' CASCADE'';
END IF;
RETURN FOUND;
END;
' LANGUAGE 'plpgsql';

COMMENT ON FUNCTION dba_droptype(varchar
) IS '
Usage: SELECT dba_drop_type(type_n
ame)
Checks for existence of a type and drops it if found.
Implements DROP TYPE CASCADE; if a function or other object
depends on the type, that object will also be dropped.
Returns TRUE if successful, returns FALSE if type is
not found.';

--
Craig Addleman
DBA
ShareChive LLC

* Philippe Lang <philippe.lang@attiksystem.ch> [2005-04-06 05:59]:
> Hi,
>
> Since it is not possible to use CREATE OR REPLACE TYPE, is there a way
> of using DROP TYPE on a non-existing type, without causing the entire
> script to abort? It may sound crazy to ask for this, but it could be
> really useful in my case, where Pl/Pgsql and Pl/Perl code is being
> generated automatically, based on data found in a database.
>
> Thanks
>
> -----------------
> Philippe Lang
>
>
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