gistfile1.sql

-- Source: http://archives.postgresql.org/pgsql-sql/2005-08/msg00046.php
-- Thanks: http://archives.postgresql.org/pgsql-es-ayuda/2008-02/msg00293.php

CREATE FUNCTION count_estimate(query text) RETURNS integer AS $$
DECLARE
    rec   record;
    rows  integer;
BEGIN
    FOR rec IN EXECUTE 'EXPLAIN ' || query LOOP
        rows := substring(rec."QUERY PLAN" FROM ' rows=([[:digit:]]+)');
        EXIT WHEN rows IS NOT NULL;
    END LOOP;

    RETURN rows;
END;
$$ LANGUAGE plpgsql IMMUTABLE STRICT;