-- Name: canon_sql(text, regtype); Type: FUNCTION; Schema: util; Owner: -

--

CREATE FUNCTION canon_sql(expr text, table_ regtype DEFAULT NULL::regtype) RETURNS text

    LANGUAGE sql STABLE

    AS $_$

SELECT util.trim_parens((regexp_matches(line,

	'^  Filter: \((.*) IS DISTINCT FROM result_type_null\)$'))[1])

FROM util.explain($$

-- declare types (use WITH to avoid `types.` prefix)

WITH types AS

(

	SELECT

	  NULL::$$||util.typeof(expr, table_)||$$ AS result_type_null

	, /*col types:*/(NULL::$$||table_||$$).*

)

SELECT * FROM types WHERE ($$||expr||$$) IS DISTINCT FROM result_type_null

	/* can't just use IS NOT NULL, or even `= result_type_null`, because these

	will simplify NULL exprs too far */

$$) line

LIMIT 1

$_$;

--