MDEV-21195 INSERT chooses wrong partition for RANGE partitioning by DECIMAL column

Use FLOOR rounding for DECIMAL_RESULT item_expr in partition function.

3 files changed, 26 insertions, 6 deletions

diff --git a/sql/my_decimal.cc b/sql/my_decimal.cc
index 01fad3dde37..8acb46b9ef2 100644
--- a/sql/my_decimal.cc
+++ b/sql/my_decimal.cc
@@ -345,12 +345,12 @@ void my_decimal_trim(ulonglong *precision, uint *scale)
 */
 
 int my_decimal2int(uint mask, const decimal_t *d, bool unsigned_flag,
-		   longlong *l)
+		   longlong *l, decimal_round_mode round_type)
 {
   int res;
   my_decimal rounded;
   /* decimal_round can return only E_DEC_TRUNCATED */
-  decimal_round(d, &rounded, 0, HALF_UP);
+  decimal_round(d, &rounded, 0, round_type);
   res= (unsigned_flag ?
         decimal2ulonglong(&rounded, (ulonglong *) l) :
         decimal2longlong(&rounded, l));
diff --git a/sql/my_decimal.h b/sql/my_decimal.h
index 6d6bb258293..b409a87bdd4 100644
--- a/sql/my_decimal.h
+++ b/sql/my_decimal.h
@@ -348,7 +348,7 @@ my_decimal *seconds2my_decimal(bool sign, ulonglong sec, ulong microsec,
                         (TIME)->second_part, (DECIMAL))
 
 int my_decimal2int(uint mask, const decimal_t *d, bool unsigned_flag,
-		   longlong *l);
+		   longlong *l, decimal_round_mode round_type= HALF_UP);
 
 inline
 int my_decimal2double(uint, const decimal_t *d, double *result)
diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index 00a78ce3199..febd88c4b9b 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -2840,14 +2840,34 @@ bool partition_key_modified(TABLE *table, const MY_BITMAP *fields)
 
 static inline int part_val_int(Item *item_expr, longlong *result)
 {
-  *result= item_expr->val_int();
+  switch (item_expr->cmp_type())
+  {
+  case DECIMAL_RESULT:
+  {
+    my_decimal buf;
+    my_decimal *val= item_expr->val_decimal(&buf);
+    if (val && my_decimal2int(E_DEC_FATAL_ERROR, val, item_expr->unsigned_flag,
+                              result, FLOOR) != E_DEC_OK)
+      return true;
+    break;
+  }
+  case INT_RESULT:
+    *result= item_expr->val_int();
+    break;
+  case STRING_RESULT:
+  case REAL_RESULT:
+  case ROW_RESULT:
+  case TIME_RESULT:
+    DBUG_ASSERT(0);
+    break;
+  }
   if (item_expr->null_value)
   {
     if (unlikely(current_thd->is_error()))
-      return TRUE;
+      return true;
     *result= LONGLONG_MIN;
   }
-  return FALSE;
+  return false;
 }