Return SETOF rows from PostgreSQL function

Question

I have a situation where I want to return the join between two views. and that\'s a lot of columns. It was pretty easy in sql server. But in PostgreSQL when I do the join. I

Answer 1

Sanitize function

The manual has all the basics for PL/pgSQL. Basically, what you have can be simplified / sanitized to:

CREATE OR REPLACE FUNCTION func_a(username text = '', databaseobject text = '')
  RETURNS ???? AS
$func$
BEGIN

RETURN QUERY EXECUTE
format ('SELECT * FROM %s v1 LEFT JOIN %I v2 USING (id)'
       , CASE WHEN username = '*' THEN 'view1' ELSE 'view3' END, databaseobject);

END
$func$  LANGUAGE plpgsql;

• You don't need additional instances of BEGIN .. END in the function body except to start a separate code block with its own scope, which is rarely needed.

• The standard SQL concatenation operator is ||. + is a "creative" addition of your former vendor.

• Don't use CaMeL-case identifiers unless you double-quote them. Best you don't use them at all:

• Are PostgreSQL column names case-sensitive?

• varchar(4000) is also tailored to a specific limitation of SQL Server. This data type has no performance benefit whatsoever in Postgres. Only use it if you actually need a limit of 4000 characters. I would just use text - except that we don't need any variables at all here, after I simplified the function.

• If you have not used format(), yet, consult the manual here.

Return type

Now, for your actual question: The return type for a dynamic query is a bit tricky, since SQL requires the function to return a well defined type. If you have a table or view or composite type in your database already that matches the column definition list you want to return you can just use that:

CREATE FUNCTION foo()
  RETURNS SETOF my_view AS
...

If you are making the type up as you go, you can either return anonymous records:

CREATE FUNCTION foo()
  RETURNS SETOF record AS
...

or provide a column definition list with (simplest) RETURNS TABLE:

CREATE FUNCTION foo()
  RETURNS TABLE (col1 int, col2 text, ...) AS
...

The downside for anonymous records: you then have to provide a column definition list with every call, so I hardly ever use that.

I wouldn't use SELECT * to begin with. Use a definitive list of columns to return and declare your return type accordingly:

CREATE OR REPLACE FUNCTION func_a(username text = '', databaseobject text = '')
  RETURNS TABLE(col1 int, col2 text, col3 date) AS
$func$
BEGIN

RETURN QUERY EXECUTE
format ($f$SELECT v1.col1, v1.col2, v2.col3
           FROM %s v1 LEFT JOIN %I v2 USING (id)$f$
       , CASE WHEN username = '*' THEN 'view1' ELSE 'view3' END, databaseobject);

END
$func$ LANGUAGE plpgsql;

For completely dynamic queries, I'd rather use a plain SQL query to begin with. Not a function.

There are more advanced options, but you may need to study the basics first.

• Refactor a PL/pgSQL function to return the output of various SELECT queries