Execute query passed in argument in Postgresql - sql

Question

I'm learning plpgsql and I have an exercise where I have to check if a query passed in function argument raises an exception or not and for that I need to run that query but I have no idea how to that.
For the moment I have this :
CREATE OR REPLACE FUNCTION exec(query varchar(100)) RETURNS BOOLEAN AS $$
BEGIN
BEGIN
raise notice 'query : %', query;
PERFORM query;
return 1;
EXCEPTION
when undefined_table then
raise notice 'undefined table';
WHEN undefined_column THEN
raise notice 'undefined column';
WHEN foreign_key_violation THEN
raise notice 'foreign key violation ';
WHEN syntax_error THEN
raise notice 'syntaxe error';
END;
return 0;
END
$$ LANGUAGE PLPGSQL;
Right now the problem I have is with the 5th line. It's where I'd want to perform the query to catch an error and then return 1 if no exception is caught or else return 0 after the "END" if there's an error.
Thank you for your help!

Answer 1

You cannot to execute dynamic query by statement PERFORM. You should to use statement EXECUTE.
CREATE OR REPLACE FUNCTION exec(query text)
RETURNS BOOLEAN
AS $$
BEGIN
RAISE NOTICE 'query : %', query;
EXECUTE query;
RETURN true;
EXCEPTION
WHEN when undefined_table THEN
RAISE NOTICE 'undefined table';
WHEN undefined_column THEN
RAISE NOTICE 'undefined column';
WHEN foreign_key_violation THEN
RAISE NOTICE 'foreign key violation ';
WHEN syntax_error THEN
RAISE NOTICE 'syntax error';
RETURN false;
END;
$$ LANGUAGE PLPGSQL;
Good start for programming in PL/pgSQL is reading related documentation. It has only few pages. The programming of stored procedures in PL/pgSQL is partially different from application's programming or from programming of stored procedures in other RDBMS.