message: test cardinality function
diff: @@ -16,4 +16,42 @@ SELECT CARDINALITY(HISTOGRAM(val)) FROM src AS t(k, val);
  ----
  NULL
  +statement ok
  +CREATE TABLE t1 AS (SELECT ARRAY[(1, 'x'), (2, 'y'), (4, 's')] AS list);
  +
  +statement ok
  +INSERT INTO t1 VALUES (ARRAY[(2, 'a'), (3,'b')]);
  +
  +statement ok
  +INSERT INTO t1 VALUES (ARRAY[NULL, NULL]);
  +
  +statement ok
  +INSERT INTO t1 VALUES (ARRAY[NULL, (7,'g')]);
  +
  +statement ok
  +INSERT INTO t1 VALUES (ARRAY[NULL, NULL]);
  +
  +statement ok
  +INSERT INTO t1 VALUES (NULL);
  +
  +query I
  +SELECT MAP_FROM_ENTRIES(list) FROM t1;
  +----
  +{1=x, 2=y, 4=s}
  +{2=a, 3=b}
  +NULL
  +{7=g}
  +NULL
  +NULL
  +
  +query I
  +SELECT CARDINALITY(MAP_FROM_ENTRIES(list)) FROM t1;
  +----
  +3
  +2
  +NULL
  +1
  +NULL
  +NULL
  +
  