How Can I Efficiently Implement Parameterized ORDER BY and LIMIT Clauses in a PostgreSQL Table Function?

PostgreSQL Parameterized Order By / Limit in Table Function

The question explores options for incorporating order by and limit clauses within a PostgreSQL table function, highlighting the potential inefficiency of ordering and slicing outside the function.

One solution presented is the use of a plpgsql function, which allows for more complex query construction and execution via EXECUTE. This approach offers greater flexibility and control over the query.

To implement this, a modified plpgsql function can be created:

CREATE OR REPLACE FUNCTION get_stuff(_param text, _orderby text, _limit int)
  RETURNS SETOF stuff AS
$func$
BEGIN
   RETURN QUERY EXECUTE '
      SELECT *
      FROM   stuff
      WHERE  col = 
      ORDER  BY ' || quote_ident(_orderby) || ' ASC
      LIMIT  '
   USING _param, _limit;
END
$func$  LANGUAGE plpgsql;

This function can be called as follows:

SELECT * FROM get_stuff('hello', 'col2', 100);

This solution avoids SQL injection vulnerabilities by using quote_ident() for identifiers and the USING clause for parameter values. Additionally, RETURN QUERY EXECUTE efficiently returns the query results.

While a plpgsql function may be more verbose than a simple SQL function, it provides greater flexibility and performance for more complex queries.

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