> CREATE OR REPLACE FUNCTION strict_min_agg (anyarray,anyelement ) > RETURNS anyarray LANGUAGE sql IMMUTABLE AS $$ > SELECT CASE > WHEN $1 IS NULL THEN ARRAY[$2] > WHEN $1[1] IS NULL THEN $1 > WHEN $2 IS NULL THEN ARRAY[$2] -- use $2 not NULL to preserve > type > ELSE ARRAY[least($1[1],$2)] END ; > $$; > > > CREATE OR REPLACE FUNCTION strict_min_final (anyarray) > RETURNS anyelement LANGUAGE sql IMMUTABLE AS $$ > SELECT CASE WHEN $1 IS NULL THEN NULL ELSE $1[1] END ; > $$; > > CREATE AGGREGATE strict_min (x anyelement) ( > sfunc = strict_min_agg, > stype = anyarray, > finalfunc = strict_min_final > ); >
It seems like this should be possible to do in something more close to O(log n). But I'm not sure how to fix the semantics with aggregates. SELECT max(<column>) FROM <table>; SELECT true FROM <table> WHERE <column> IS NULL LIMIT 1; Both these queries can be resolved with a index lookup (if one is available).
