MDEV-452 Add full support for auto-initialized/updated timestamp and datetime

Generalized support for auto-updated and/or auto-initialized timestamp
and datetime columns. This patch is a reimplementation of MySQL's
"WL#5874: CURRENT_TIMESTAMP as DEFAULT for DATETIME columns". In order to
ease future merges, this implementation reused few function and variable
names from MySQL's patch, however the implementation is quite different.

TODO:
The only unresolved problem in this patch is the semantics of LOAD DATA for
TIMESTAMP and DATETIME columns in the cases when there are missing or NULL
columns. I couldn't fully comprehend the logic behind MySQL's behavior and
its relationship with their own documentation, so I left the results to be
more consistent with all other LOAD cases.

The problematic test cases can be seen by running the test file function_defaults,
and observing the test case differences. Those were left on purpose for discussion.

1 files changed, 2 insertions, 20 deletions

diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index b3f97d35033..5f58247a79d 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -3451,8 +3451,8 @@ void ha_partition::try_semi_consistent_read(bool yes)
 
     ADDITIONAL INFO:
 
-    We have to set timestamp fields and auto_increment fields, because those
-    may be used in determining which partition the row should be written to.
+    We have to set auto_increment fields, because those may be used in
+    determining which partition the row should be written to.
 */
 
 int ha_partition::write_row(uchar * buf)
@@ -3463,7 +3463,6 @@ int ha_partition::write_row(uchar * buf)
   bool have_auto_increment= table->next_number_field && buf == table->record[0];
   my_bitmap_map *old_map;
   THD *thd= ha_thd();
-  timestamp_auto_set_type saved_timestamp_type= table->timestamp_field_type;
   ulonglong saved_sql_mode= thd->variables.sql_mode;
   bool saved_auto_inc_field_not_null= table->auto_increment_field_not_null;
 #ifdef NOT_NEEDED
@@ -3472,11 +3471,6 @@ int ha_partition::write_row(uchar * buf)
   DBUG_ENTER("ha_partition::write_row");
   DBUG_ASSERT(buf == m_rec0);
 
-  /* If we have a timestamp column, update it to the current time */
-  if (table->timestamp_field_type & TIMESTAMP_AUTO_SET_ON_INSERT)
-    table->timestamp_field->set_time();
-  table->timestamp_field_type= TIMESTAMP_NO_AUTO_SET;
-
   /*
     If we have an auto_increment column and we are writing a changed row
     or a new row, then update the auto_increment value in the record.
@@ -3552,7 +3546,6 @@ int ha_partition::write_row(uchar * buf)
 exit:
   thd->variables.sql_mode= saved_sql_mode;
   table->auto_increment_field_not_null= saved_auto_inc_field_not_null;
-  table->timestamp_field_type= saved_timestamp_type;
   DBUG_RETURN(error);
 }
 
@@ -3587,18 +3580,8 @@ int ha_partition::update_row(const uchar *old_data, uchar *new_data)
   uint32 new_part_id, old_part_id;
   int error= 0;
   longlong func_value;
-  timestamp_auto_set_type orig_timestamp_type= table->timestamp_field_type;
   DBUG_ENTER("ha_partition::update_row");
 
-  /*
-    We need to set timestamp field once before we calculate
-    the partition. Then we disable timestamp calculations
-    inside m_file[*]->update_row() methods
-  */
-  if (orig_timestamp_type & TIMESTAMP_AUTO_SET_ON_UPDATE)
-    table->timestamp_field->set_time();
-  table->timestamp_field_type= TIMESTAMP_NO_AUTO_SET;
-
   if ((error= get_parts_for_update(old_data, new_data, table->record[0],
                                    m_part_info, &old_part_id, &new_part_id,
                                    &func_value)))
@@ -3672,7 +3655,6 @@ exit:
       info(HA_STATUS_AUTO);
     set_auto_increment_if_higher(table->found_next_number_field);
   }
-  table->timestamp_field_type= orig_timestamp_type;
   DBUG_RETURN(error);
 }