Re: Trigger function - variable for schema name

----- Original Message -----
> From: Glyn Astill <glynastill@yahoo.co.uk>
> To: ssylla <stefansylla@gmx.de>; "pgsql-sql@postgresql.org" <pgsql-sql@postgresql.org>
> Cc:
> Sent: Monday, 27 January 2014, 10:47
> Subject: Re: [SQL] Trigger function - variable for schema name
>
>>  From: ssylla <stefansylla@gmx.de>
>
>> To: pgsql-sql@postgresql.org
>> Sent: Monday, 27 January 2014, 8:39
>> Subject: [SQL] Trigger function - variable for schema name
>>
>>
>> Dear list,
>>
>> I have the following trigger function an try to use TG_ARGV as a variable
>> for the schema name of the table that caused the trigger:
>>
>> CREATE OR REPLACE FUNCTION trigger_function1()
>>   RETURNS trigger AS
>> $BODY$
>>     declare my_schema text;
>>     begin
>>         my_schema := TG_ARGV[0];
>>         select table2.id into new.id from my_schema.table2;
>>         new.columnx=function1(my_schema,value1);
>>      return new;
>> end:
>> $$
>> language plpgsql
>> CREATE TRIGGER trigger_function1
>>   BEFORE INSERT
>>   ON schema1.table1
>>   FOR EACH ROW
>>   EXECUTE PROCEDURE trigger_function1('schema1');
>>
>> Using the trigger I get the following message:
>> ERROR: schema "my_schema" does not exist
>>
>
> To do what you're trying to do there you'd probably be best to use
> EXECUTE:
>
> CREATE OR REPLACE FUNCTION trigger_function1()
>   RETURNS trigger AS
> $BODY$
>     declare my_schema text;
>     begin
>         my_schema := TG_ARGV[0];
>         EXECUTE 'select table2.id into new.id from ' ||
> quote_ident(my_schema) || '.table2';

Oops, missed the select into there, and you only want that query to return one record:

EXECUTE 'select table2.id from ' || quote_ident(my_schema) || '.table2' into new.id;

>
>         new.columnx=function1(my_schema,value1);
>     return new;
> end:
> $$
> language plpgsql
>
>
>> So far I tried another option by temporarily changing the search path, but
>> that might cause problems with other users who are working on other schemas
>> of the database at the same time. That's why I would like to write the
>> trigger in a way that it will only perform on the specified schema, but not
>> changing the global search_path of the database.
>> I also tried using dynamic sql with "execute format('...',
> TG_TABLE_SCHEMA);
>> but that will only work inside the trigger, not if I want to pass the schema
>> name to another function that is called from within the trigger.
>
>
> We'll I don't see why you couldn't pull the current schema with
> TG_TABLE_SCHEMA and pass it as a variable to your other function, but I'm
> not entirely sure what you're trying to do to be honest.
>