--echo #

--echo # MDEV-17979 Assertion `0' failed in Item::val_native upon SELECT with timestamp, NULLIF, GROUP BY
--echo #

1 files changed, 56 insertions, 0 deletions

diff --git a/sql/item.h b/sql/item.h
index 5d0f2cd43f5..9c53f731f6e 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -6021,6 +6021,62 @@ public:
 };
 
 
+/**
+  We need a separate class Item_copy_timestamp because
+  TIMESTAMP->string->TIMESTAMP conversion is not round trip safe
+  near the DST change, e.g. '2010-10-31 02:25:26' can mean:
+   - my_time_t(1288477526) - summer time in Moscow
+   - my_time_t(1288481126) - winter time in Moscow, one hour later
+*/
+class Item_copy_timestamp: public Item_copy
+{
+  Timestamp_or_zero_datetime m_value;
+public:
+  Item_copy_timestamp(THD *thd, Item *arg): Item_copy(thd, arg) { }
+  const Type_handler *type_handler() const { return &type_handler_timestamp2; }
+  void copy()
+  {
+    Timestamp_or_zero_datetime_native_null tmp(current_thd, item, false);
+    null_value= tmp.is_null();
+    m_value= tmp.is_null() ? Timestamp_or_zero_datetime() :
+                             Timestamp_or_zero_datetime(tmp);
+  }
+  int save_in_field(Field *field, bool no_conversions)
+  {
+    Timestamp_or_zero_datetime_native native(m_value, decimals);
+    return native.save_in_field(field, decimals);
+  }
+  longlong val_int()
+  {
+    return m_value.to_datetime(current_thd).to_longlong();
+  }
+  double val_real()
+  {
+    return m_value.to_datetime(current_thd).to_double();
+  }
+  String *val_str(String *to)
+  {
+    return m_value.to_datetime(current_thd).to_string(to, decimals);
+  }
+  my_decimal *val_decimal(my_decimal *to)
+  {
+    return m_value.to_datetime(current_thd).to_decimal(to);
+  }
+  bool get_date(THD *thd, MYSQL_TIME *ltime, date_mode_t fuzzydate)
+  {
+    bool res= m_value.to_TIME(thd, ltime, fuzzydate);
+    DBUG_ASSERT(!res);
+    return res;
+  }
+  bool val_native(THD *thd, Native *to)
+  {
+    return m_value.to_native(to, decimals);
+  }
+  Item *get_copy(THD *thd)
+  { return get_item_copy<Item_copy_timestamp>(thd, this); }
+};
+
+
 /*
   Cached_item_XXX objects are not exactly caches. They do the following: