array_append_distinct, array_erase函数

CREATE OR REPLACE FUNCTION array_append_distinct(anyarray, anyelement) 
RETURNS anyarray AS $$ 
  SELECT ARRAY(SELECT unnest($1) union SELECT $2) 
$$ LANGUAGE sql;

postgres=# select array_append_distinct(array[1,2,3,4],1);
 array_append_distinct 
-----------------------
 {1,2,3,4}
(1 row)

postgres=# select array_append_distinct(array[1,2,3,4],7);
 array_append_distinct 
-----------------------
 {1,2,3,4,7}
(1 row)

CREATE OR REPLACE FUNCTION array_erase(anyarray, anyelement) 
RETURNS anyarray AS $$
  SELECT ARRAY(SELECT v FROM unnest($1) g(v) WHERE v <> $2)
$$ LANGUAGE sql;

postgres=# select array_erase(array[1,2,3,2,5], 2);
 array_erase 
-------------
 {1,3,5}
(1 row)

postgres=# select array_erase(array[1,2,3,2,5], 1);
 array_erase 
-------------
 {2,3,2,5}
(1 row)