Array slice for PostgreSQL

slice.sql

-- Copyright 2016, Miles Elam <[email protected]>
-- MIT License, http://www.opensource.org/licenses/mit-license.php
 
CREATE OR REPLACE FUNCTION splice(target anyarray, start integer, to_insert anyarray)
RETURNS anyarray LANGUAGE 'sql' IMMUTABLE LEAKPROOF STRICT AS $$
  SELECT target[0:start - 1]
      || to_insert
      || target[start:array_length(target, 1)]
$$;

COMMENT ON FUNCTION splice(anyarray, integer, anyarray)
    IS 'E.g., SELECT splice(''{6,9,4,2,5}''::integer[], 3, ''{3,1}''::integer[]);
returns {6,9,3,1,4,2,5}';

CREATE OR REPLACE FUNCTION splice(target anyarray, start integer, to_insert anyelement)
RETURNS anyarray LANGUAGE 'sql' IMMUTABLE LEAKPROOF STRICT AS $$
  SELECT splice(target, start, ARRAY[to_insert]);
$$;

COMMENT ON FUNCTION splice(anyarray, integer, anyelement)
    IS 'E.g., SELECT splice(''{6,9,4,2,5}''::integer[], 3, 1);
returns {6,9,1,4,2,5}';

CREATE OR REPLACE FUNCTION splice(target anyarray, start integer, delete_count integer, to_insert anyarray)
RETURNS anyarray LANGUAGE 'sql' IMMUTABLE LEAKPROOF STRICT AS $$
  SELECT target[0:start - 1]
      || to_insert
      || target[start + delete_count:array_length(target, 1)]
$$;

COMMENT ON FUNCTION splice(anyarray, integer, integer, anyarray)
    IS 'E.g., SELECT splice(''{6,9,4,2,5}''::integer[], 3, ''{3,1}''::integer[]);
returns {6,9,3,1,5}';

CREATE OR REPLACE FUNCTION splice(target anyarray, start integer, delete_count integer, to_insert anyelement)
RETURNS anyarray LANGUAGE 'sql' IMMUTABLE LEAKPROOF STRICT AS $$
  SELECT splice(target, start, delete_count, ARRAY[to_insert]);
$$;

COMMENT ON FUNCTION splice(anyarray, integer, integer, anyelement)
    IS 'E.g., SELECT splice(''{6,9,4,2,5}''::integer[], 3, 2, 1);
returns {6,9,1,5}';