Don't emit non-canonical empty arrays in array_remove().

Dean Rasheed

src/backend/utils/adt/arrayfuncs.c

@@ -5398,6 +5398,14 @@ array_replace_internal(ArrayType *array,
 		return array;
 	}
 
+	/* If all elements were removed return an empty array */
+	if (nresult == 0)
+	{
+		pfree(values);
+		pfree(nulls);
+		return construct_empty_array(element_type);
+	}
+
 	/* Allocate and initialize the result array */
 	if (hasnulls)
 	{

src/test/regress/expected/arrays.out

@@ -1577,6 +1577,12 @@ select array_remove(array['A','CC','D','C','RR'], 'RR');
 
 select array_remove('{{1,2,2},{1,4,3}}', 2); -- not allowed
 ERROR:  removing elements from multidimensional arrays is not supported
+select array_remove(array['X','X','X'], 'X') = '{}';
+ ?column? 
+----------
+ t
+(1 row)
+
 select array_replace(array[1,2,5,4],5,3);
  array_replace 
 ---------------

src/test/regress/sql/arrays.sql

@@ -438,6 +438,7 @@ select array_remove(array[1,2,2,3], 5);
 select array_remove(array[1,NULL,NULL,3], NULL);
 select array_remove(array['A','CC','D','C','RR'], 'RR');
 select array_remove('{{1,2,2},{1,4,3}}', 2); -- not allowed
+select array_remove(array['X','X','X'], 'X') = '{}';
 select array_replace(array[1,2,5,4],5,3);
 select array_replace(array[1,2,5,4],5,NULL);
 select array_replace(array[1,2,NULL,4,NULL],NULL,5);