Presto SQL Generic Structure for sorting an array by another array

array_sort_by.sql

-- LINES 1 - 4: Transform(  to x -> ELEMENT_AT
-- The TRANSFORM orders the array by a transform of the array.
-- Channel Array is of form A#T :: String, where T :: Integral
-- RESULT: An ordered array :: Integral, which will form our keys for the second section.

-- LINES 5 - 11: ELEMENT_AT( to END
-- We now take our keys one by one, and use them in ELEMENT_AT(mapping, key) to generate a new array. 
-- As our keys are in the right order, our end array will also be. (Duplicate keys will cause a missing hit.)
-- The other lines generate the actual map.
-- RESULT: An ordered array. 
WITH 
  
  ARRAY_SORT_BY AS (
    SELECT
	TRANSFORM(
		ARRAY_SORT(
				TRANSFORM(ARRAY_A, x -> CAST(REGEXP_EXTRACT(x, '#(.*)', 1) AS BIGINT))
				),
		x -> ELEMENT_AT(
			MAP(
				TRANSFORM(ARRAY_A, x -> CAST(REGEXP_EXTRACT(x, '#(.*)', 1) AS BIGINT)), 
				ARRAY_A
				), 
				x)
		)
	)
              
SELECT * FROM ARRAY_SORT_BY