[8.1] "drop table" in plpgsql function

---------- Forwarded message ----------
From: Sergey Karin <sergey.karin@gmail.com>
Date: 11.11.2005 13:59
Subject: [8.1] "drop table" in plpgsql function
To: pgsql-general@postgresql.org

hi all!

I have found a strange error.

panorama2=# select version();
version
------------------------------------------------------------------------
PostgreSQL 8.1.0 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.3
(1 row)

I have next function in file ./f_safe_drop_table.sql:
------------------------------
create or replace function f_safe_drop_table(varchar) returns bool as'
declare
table_name alias for $1;
tcount int4;
begin
select f_is_table_exist(table_name) into tcount;
if(tcount > 0) then
drop table table_name;
return true;
end if;
return false;
end
'language 'plpgsql';
======================

when I create my function in psql, I have next error:
-----------------------
panorama2=# \i ./f_safe_drop_table.sql
psql:./f_safe_drop_table.sql:29: ERROR: syntax error at or near "$1"
at character 13
QUERY: drop table $1
CONTEXT: SQL statement in PL/PgSQL function "f_safe_drop_table" near line 10
psql:./Functions/Misc/f_safe_drop_table.sql:29: LINE 1: drop table $1
psql:./Functions/Misc/f_safe_drop_table.sql:29: ^
-----------------------

But if I replace "drop table table_name" on "dyn_query := 'drop table
' || table_name; execute dyn_query" all works fine!
------------------------------
create or replace function f_safe_drop_table(varchar) returns bool as'
declare
table_name alias for $1;
tcount int4;
dyn_query varchar;
begin
select f_is_table_exist(table_name) into tcount;
if(tcount > 0) then
dyn_query := 'drop table ' || table_name;
execute dyn_query;
return true;
end if;
return false;
end
'language 'plpgsql';
======================

panorama2=# \i ./f_safe_drop_table.sql
CREATE FUNCTION

Also both functions on PG8.0 works fine!

Sergey Karin

Sergey,

On Nov 14, 2005, at 2:03 AM, Sergey Karin wrote:

I have found a strange error.

Perhaps your f_is_table_exist function is not working correctly.

Using variables for table references is not supported in plpgsql (any
version). You must use execute. Here is my test on 8.0.4:

create table test_table(a text, b integer);

create or replace function del_table(varchar) returns boolean as '
declare
tname alias for $1;
begin
drop table tname;
return true;
end;
' language plpgsql;

select del_table('test_table');

CREATE TABLE
CREATE FUNCTION
psql:16: ERROR: syntax error at or near "$1" at character 13
QUERY: drop table $1
CONTEXT: PL/pgSQL function "del_table" line 4 at SQL statement
psql:16: LINE 1: drop table $1
psql:16:

It works Ok if you change the drop line to

execute ''drop table '' || tname;

Also, the example that you indicate is working with execute is not
quoted correctly.

Best,

John DeSoi, Ph.D.
http://pgedit.com/
Power Tools for PostgreSQL