MDEV-21319 COUNT(*) returns 1, actual SELECT returns no result in 10.3.21, but 1 result in 10.1.41

Item_ref::val_(datetime|time)_packed() erroneously called
(*ref)->val_(datetime|time)_packed().

- Fixing to call (*ref)->val_(datetime|time)_packed_result().
- Backporting Item::val_(datetime|time)_packed_result() from 10.3.
- Fixing Item_field::get_date_result() to handle null_value in the same
  way how Item_field::get_date() does.

2 files changed, 26 insertions, 5 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 86bd4670714..17eb570ad80 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -145,6 +145,19 @@ bool Item::get_date_with_conversion(MYSQL_TIME *ltime, ulonglong fuzzydate)
 }
 
 
+longlong Item::val_datetime_packed_result()
+{
+  MYSQL_TIME ltime, tmp;
+  if (get_date_result(&ltime, TIME_FUZZY_DATES | TIME_INVALID_DATES))
+    return 0;
+  if (ltime.time_type != MYSQL_TIMESTAMP_TIME)
+    return pack_time(&ltime);
+  if ((null_value= time_to_datetime_with_warn(current_thd, &ltime, &tmp, 0)))
+    return 0;
+  return pack_time(&tmp);
+}
+
+
 /**
   Get date/time/datetime.
   If DATETIME or DATE result is returned, it's converted to TIME.
@@ -2594,12 +2607,13 @@ bool Item_field::get_date(MYSQL_TIME *ltime,ulonglong fuzzydate)
 
 bool Item_field::get_date_result(MYSQL_TIME *ltime, ulonglong fuzzydate)
 {
-  if (result_field->is_null() || result_field->get_date(ltime,fuzzydate))
+  if ((null_value= result_field->is_null()) ||
+      result_field->get_date(ltime, fuzzydate))
   {
     bzero((char*) ltime,sizeof(*ltime));
-    return (null_value= 1);
+    return true;
   }
-  return (null_value= 0);
+  return false;
 }
 
 
@@ -7313,7 +7327,7 @@ bool Item_ref::get_date(MYSQL_TIME *ltime,ulonglong fuzzydate)
 longlong Item_ref::val_datetime_packed()
 {
   DBUG_ASSERT(fixed);
-  longlong tmp= (*ref)->val_datetime_packed();
+  longlong tmp= (*ref)->val_datetime_packed_result();
   null_value= (*ref)->null_value;
   return tmp;
 }
@@ -7322,7 +7336,7 @@ longlong Item_ref::val_datetime_packed()
 longlong Item_ref::val_time_packed()
 {
   DBUG_ASSERT(fixed);
-  longlong tmp= (*ref)->val_time_packed();
+  longlong tmp= (*ref)->val_time_packed_result();
   null_value= (*ref)->null_value;
   return tmp;
 }
diff --git a/sql/item.h b/sql/item.h
index fb11064f122..bea09620ef8 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -1302,6 +1302,13 @@ public:
     uint fuzzydate= TIME_FUZZY_DATES | TIME_INVALID_DATES | TIME_TIME_ONLY;
     return get_date(&ltime, fuzzydate) ? 0 : pack_time(&ltime);
   }
+  longlong val_datetime_packed_result();
+  longlong val_time_packed_result()
+  {
+    MYSQL_TIME ltime;
+    uint fuzzydate= TIME_TIME_ONLY | TIME_INVALID_DATES | TIME_FUZZY_DATES;
+    return get_date_result(&ltime, fuzzydate) ? 0 : pack_time(&ltime);
+  }
   // Get a temporal value in packed DATE/DATETIME or TIME format
   longlong val_temporal_packed(enum_field_types f_type)
   {