lp:731124 Loss of precision on DISTINCT

many changes:
* NOT_FIXED_DEC now create hires fields, not old ones.
  As a result, temp tables preserve microseconds (on DISTINCT, GROUP BY)
* I_S tables force decimals=0 on temporal types (backward compatibility)
* Item_func_coalesce calculates decimals for temporal types
* no precision for TIME/DATETIME in CAST means 0, not NOT_FIXED_DEC
* addtime/timediff calculate decimals from arguments (not NOT_FIXED_DEC)

sql/field.h:
  NOT_FIXED_DEC now create hires fields, not old ones
sql/item.h:
  force decimals=0 for I_S tables
sql/item_cmpfunc.cc:
  Item_func_coalesce calculates decimals for temporal types
sql/item_create.cc:
  no precision for TIME/DATETIME in CAST means 0, not NOT_FIXED_DEC
sql/item_timefunc.cc:
  addtime calculates decimals from arguments (not NOT_FIXED_DEC)
sql/item_timefunc.h:
  timediff calculates decimals from arguments (not NOT_FIXED_DEC)

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index 36be86cd89c..b28daed202b 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -765,7 +765,7 @@ public:
   const char *func_name() const { return "timediff"; }
   void fix_length_and_dec()
   {
-    decimals= NOT_FIXED_DEC;
+    decimals= max(args[0]->decimals, args[1]->decimals);
     Item_timefunc::fix_length_and_dec();
     maybe_null= 1;
   }