mdim_array_postgresql.sql

CREATE OR REPLACE FUNCTION contents.reduce_dim(ANYARRAY)
  RETURNS SETOF ANYARRAY AS
  $function$
  DECLARE
    s $1%TYPE;
  BEGIN
    FOREACH s SLICE 1 IN ARRAY $1 LOOP
      RETURN NEXT s;
    END LOOP;
    RETURN;
  END;
  $function$
LANGUAGE plpgsql IMMUTABLE;

CREATE AGGREGATE compound_array (
BASETYPE = ANYARRAY,
STYPE = ANYARRAY,
SFUNC = ARRAY_CAT,
INITCOND = '{}'
);

CREATE OR REPLACE FUNCTION contents.except_dim(a ANYARRAY, b ANYARRAY)
  RETURNS ANYARRAY AS
  $function$
  DECLARE
    c $1%TYPE;
  BEGIN
    WITH merge AS (
      SELECT
        contents.reduce_dim(a) AS dim
      EXCEPT
      SELECT
        contents.reduce_dim(b) AS dim
    )
    SELECT
      compound_array(ARRAY [dim])
    FROM merge
    INTO c;
    RETURN c;
  END;
  $function$
LANGUAGE plpgsql IMMUTABLE;


CREATE OR REPLACE FUNCTION contents.intersect_dim(a ANYARRAY, b ANYARRAY)
  RETURNS ANYARRAY AS
  $function$
  DECLARE
    c $1%TYPE;
  BEGIN
    WITH merge AS (
      SELECT
        contents.reduce_dim(a) AS dim
      INTERSECT 
      SELECT
        contents.reduce_dim(b) AS dim
    )
    SELECT
      compound_array(ARRAY [dim])
    FROM merge
    INTO c;
    RETURN c;
  END;
  $function$
LANGUAGE plpgsql IMMUTABLE;