Hello I thing so there are lot of aggregates based on generating array. We have fast array_agg function, but we cannot be same effective with custom aggregates. So my proposal is creating some new kind of aggregates, that are based on arrays. The primary goal is getting same speed as array_agg has.
Example: Median - http://wiki.postgresql.org/wiki/Aggregate_Median CREATE OR REPLACE FUNCTION _final_median(numeric[]) RETURNS numeric AS $$ SELECT AVG(val) FROM ( SELECT val FROM unnest($1) val ORDER BY 1 LIMIT 2 - MOD(array_upper($1, 1), 2) OFFSET CEIL(array_upper($1, 1) / 2.0) - 1 ) sub; $$ LANGUAGE 'sql' IMMUTABLE; CREATE AGGREGATE median(numeric) ( SFUNC=array_append, STYPE=_numeric[], FINALFUNC=_final_median, INITCOND='{}' ); This function is slower than array_agg because we use sfunc array_append. If could to use array_agg as base with enhancing final function then we could this task faster. Regards Pavel Stehule -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
