Postgres 14

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CREATE OR REPLACE AGGREGATE median (anyelement)
( SFUNC = array_append
, STYPE = anyarray
, INITCOND = '{}'
) ;

ERROR:  function array_append(anyarray, anyelement) does not exist

SELECT median(x.y) FROM (VALUES (1),(2),(3),(4),(5)) AS x(y)

ERROR:  function median(integer) does not exist
LINE 1: SELECT median(x.y) FROM (VALUES (1),(2),(3),(4),(5)) AS x(y)
               ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

CREATE OR REPLACE AGGREGATE median (anycompatible)
( SFUNC = array_append
, STYPE = anycompatiblearray
, INITCOND = '{}'
) ;

CREATE AGGREGATE

SELECT median(x.y) FROM (VALUES (1),(2),(3),(4),(5)) AS x(y)

median

{1,2,3,4,5}

SELECT 1