Fix for bug #30782: Truncated UNSIGNED BIGINT columns only in SELECT w/ CASE,

JOIN, and ORDER BY

Problem: improper maximum length calculation of the CASE function leads to 
decimal value truncation (storing/retrieving decimal field values).

Fix: accurately calculate maximum length/unsigned flag/decimals parameters 
of the CASE function.


mysql-test/r/case.result:
  Fix for bug #30782: Truncated UNSIGNED BIGINT columns only in SELECT w/ CASE, 
  JOIN, and ORDER BY
    - test result.
mysql-test/t/case.test:
  Fix for bug #30782: Truncated UNSIGNED BIGINT columns only in SELECT w/ CASE, 
  JOIN, and ORDER BY
    - test case.
sql/item_cmpfunc.cc:
  Fix for bug #30782: Truncated UNSIGNED BIGINT columns only in SELECT w/ CASE, 
  JOIN, and ORDER BY
    - accurately calculate Item_func_case::max_length/unsigned_flag/decimals.
sql/item_cmpfunc.h:
  Fix for bug #30782: Truncated UNSIGNED BIGINT columns only in SELECT w/ CASE, 
  JOIN, and ORDER BY
    - accurately calculate Item_func_case::max_length/unsigned_flag/decimals.

1 files changed, 30 insertions, 6 deletions

diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 86eb10d50b0..8cbbc115922 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -2530,6 +2530,23 @@ bool Item_func_case::fix_fields(THD *thd, Item **ref)
 }
 
 
+void Item_func_case::agg_str_lengths(Item* arg)
+{
+  set_if_bigger(max_length, arg->max_length);
+  set_if_bigger(decimals, arg->decimals);
+  unsigned_flag= unsigned_flag && arg->unsigned_flag;
+}
+
+
+void Item_func_case::agg_num_lengths(Item *arg)
+{
+  uint len= my_decimal_length_to_precision(arg->max_length, arg->decimals,
+                                           arg->unsigned_flag) - arg->decimals;
+  set_if_bigger(max_length, len); 
+  set_if_bigger(decimals, arg->decimals);
+  unsigned_flag= unsigned_flag && arg->unsigned_flag; 
+}
+
 
 void Item_func_case::fix_length_and_dec()
 {
@@ -2579,15 +2596,22 @@ void Item_func_case::fix_length_and_dec()
   
   max_length=0;
   decimals=0;
-  for (uint i=0 ; i < ncases ; i+=2)
+  unsigned_flag= TRUE;
+  if (cached_result_type == STRING_RESULT)
   {
-    set_if_bigger(max_length,args[i+1]->max_length);
-    set_if_bigger(decimals,args[i+1]->decimals);
+    for (uint i= 0; i < ncases; i+= 2)
+      agg_str_lengths(args[i + 1]);
+    if (else_expr_num != -1)
+      agg_str_lengths(args[else_expr_num]);
   }
-  if (else_expr_num != -1) 
+  else
   {
-    set_if_bigger(max_length,args[else_expr_num]->max_length);
-    set_if_bigger(decimals,args[else_expr_num]->decimals);
+    for (uint i= 0; i < ncases; i+= 2)
+      agg_num_lengths(args[i + 1]);
+    if (else_expr_num != -1) 
+      agg_num_lengths(args[else_expr_num]);
+    max_length= my_decimal_precision_to_length(max_length + decimals, decimals,
+                                               unsigned_flag);
   }
 }