message: Disallow non-const separators in stringagg
diff: @@ -33,12 +33,5 @@ select j, s, string_agg(s, '|') over (partition by j order by s) from a order by
  2 5 2|5
  # different separator per group
  -query III
  +statement error
  select j, s, string_agg(s, sep) over (partition by j order by s) from a order by j, s;
  -----
  -0 3 3
  -0 6 3-6
  -1 1 1
  -1 4 1|4
  -2 2 2
  -2 5 2|5
  