Fix for bug #54459: Assertion failed: param.sort_length,

file .\filesort.cc, line 149 (part II)

Problem: the server didn't disregard sort order 
for some zero length tuples.

Fix: skip sort order in such a case 
(zero length NOT NULL string functions).


mysql-test/r/select.result:
  Fix for bug #54459: Assertion failed: param.sort_length, 
  file .\filesort.cc, line 149 (part II)
    - test result.
mysql-test/t/select.test:
  Fix for bug #54459: Assertion failed: param.sort_length, 
  file .\filesort.cc, line 149 (part II)
    - test case.
sql/sql_select.cc:
  Fix for bug #54459: Assertion failed: param.sort_length, 
  file .\filesort.cc, line 149 (part II)
    - disregard sort order for zero length NOT NULL string functions
  along with zero length NOT NULL fields.

1 files changed, 13 insertions, 5 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 296b18631e5..c9cca2e601f 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -564,13 +564,21 @@ JOIN::prepare(Item ***rref_pointer_array,
     {
       Item *item= *ord->item;
       /*
-        Disregard sort order if there's only "{VAR}CHAR(0) NOT NULL" fields
-        there. Such fields don't contain any data to sort.
+        Disregard sort order if there's only 
+        zero length NOT NULL fields (e.g. {VAR}CHAR(0) NOT NULL") or
+        zero length NOT NULL string functions there.
+        Such tuples don't contain any data to sort.
       */
       if (!real_order &&
-          (item->type() != Item::FIELD_ITEM ||
-           ((Item_field *) item)->field->maybe_null() ||
-           ((Item_field *) item)->field->sort_length()))
+           /* Not a zero length NOT NULL field */
+          ((item->type() != Item::FIELD_ITEM ||
+            ((Item_field *) item)->field->maybe_null() ||
+            ((Item_field *) item)->field->sort_length()) &&
+           /* AND not a zero length NOT NULL string function. */
+           (item->type() != Item::FUNC_ITEM ||
+            item->maybe_null ||
+            item->result_type() != STRING_RESULT ||
+            item->max_length)))
         real_order= TRUE;
 
       if (item->with_sum_func && item->type() != Item::SUM_FUNC_ITEM)