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

Post-review changes according to Monty's review from 28/11/2012.

include/mysql_com.h

@@ -128,7 +128,7 @@ enum enum_server_command
                                            reserved by MySQL Cluster */
 #define FIELD_FLAGS_COLUMN_FORMAT 24    /* Field column format, bit 24-25,
                                            reserved by MySQL Cluster */
-#define HAS_EXPLICIT_DEFAULT (1 << 26) /* An INSERT/UPDATE operation supplied
+#define HAS_EXPLICIT_VALUE (1 << 26)    /* An INSERT/UPDATE operation supplied
                                           an explicit default value */
 
 #define REFRESH_GRANT		1	/* Refresh grant tables */

sql/field.cc

@@ -1817,6 +1817,10 @@ Field *Field::new_field(MEM_ROOT *root, TABLE *new_table,
   tmp->key_start.init(0);
   tmp->part_of_key.init(0);
   tmp->part_of_sortkey.init(0);
+  /*
+    TODO: it is not clear why this method needs to reset unireg_check.
+    Try not to reset it, or explain why it needs to be reset.
+  */
   tmp->unireg_check= Field::NONE;
   tmp->flags&= (NOT_NULL_FLAG | BLOB_FLAG | UNSIGNED_FLAG |
                 ZEROFILL_FLAG | BINARY_FLAG | ENUM_FLAG | SET_FLAG);
@@ -4369,16 +4373,10 @@ void Field_double::sql_type(String &res) const
   2038-01-01 00:00:00 UTC stored as number of seconds since Unix 
   Epoch in UTC.
   
-  Up to one of timestamps columns in the table can be automatically 
-  set on row update and/or have NOW() as default value.
-  TABLE::timestamp_field points to Field object for such timestamp with 
-  auto-set-on-update. TABLE::time_stamp holds offset in record + 1 for this
-  field, and is used by handler code which performs updates required.
-  
   Actually SQL-99 says that we should allow niladic functions (like NOW())
-  as defaults for any field. Current limitations (only NOW() and only 
-  for one TIMESTAMP field) are because of restricted binary .frm format 
-  and should go away in the future.
+  as defaults for any field. The current limitation (only NOW() and only 
+  for TIMESTAMP and DATETIME fields) are because of restricted binary .frm
+  format and should go away in the future.
   
   Also because of this limitation of binary .frm format we use 5 different
   unireg_check values with TIMESTAMP field to distinguish various cases of
@@ -4422,8 +4420,8 @@ Field_timestamp::Field_timestamp(uchar *ptr_arg, uint32 len_arg,
   if (unireg_check != NONE)
   {
     /*
-      This TIMESTAMP column is hereby quietly assumed to have an insert or
-      update default function.
+      We mark the flag with TIMESTAMP_FLAG to indicate to the client that
+      this field will be automaticly updated on insert.
     */
     flags|= TIMESTAMP_FLAG;
     if (unireg_check != TIMESTAMP_DN_FIELD)
@@ -4693,19 +4691,20 @@ int Field_timestamp::set_time()
     determine if there is an explicit value for each field before performing
     the data change, and call this method to mark the field.
 
-    If the 'value' parameter is NULL, then the field is marked unconditionally
-    as having an explicit value. If 'value' is not NULL, then it can be further
-    analyzed to check if it really should count as a value.
+    For timestamp columns, the only case where a column is not marked
+    as been given a value are:
+    - It's explicitly assigned with DEFAULT
+    - We assign NULL to a timestamp field that is defined as NOT NULL.
+      This is how MySQL has worked since it's start.
 */
 
 void Field_timestamp::set_explicit_default(Item *value)
 {
-  if (value &&
-      ((value->type() == Item::DEFAULT_VALUE_ITEM &&
+  if (((value->type() == Item::DEFAULT_VALUE_ITEM &&
         !((Item_default_value*)value)->arg) ||
        (!maybe_null() && value->is_null())))
     return;
-  flags|= HAS_EXPLICIT_DEFAULT;
+  set_has_explicit_value();
 }
 
 void Field_timestamp_hires::sql_type(String &res) const
@@ -5834,7 +5833,7 @@ void Field_datetime::sql_type(String &res) const
 
 int Field_datetime::set_time()
 {
-  THD *thd= current_thd;
+  THD *thd= table->in_use;
   MYSQL_TIME now_time;
   thd->variables.time_zone->gmt_sec_to_TIME(&now_time, thd->query_start());
   now_time.second_part= thd->query_start_sec_part();
@@ -8881,9 +8880,9 @@ bool Create_field::init(THD *thd, char *fld_name, enum_field_types fld_type,
   {
     /* There is a function default for insertions. */
     def= NULL;
-    unireg_check= on_update_is_function ?
+    unireg_check= (on_update_is_function ?
                    Field::TIMESTAMP_DNUN_FIELD : // for insertions and for updates.
-      Field::TIMESTAMP_DN_FIELD;    // only for insertions.
+                   Field::TIMESTAMP_DN_FIELD);   // only for insertions.
   }
   else
   {
@@ -8892,9 +8891,9 @@ bool Create_field::init(THD *thd, char *fld_name, enum_field_types fld_type,
     if (on_update_is_function)
       unireg_check= Field::TIMESTAMP_UN_FIELD; // function default for updates
     else
-      unireg_check= (fld_type_modifier & AUTO_INCREMENT_FLAG) != 0 ?
+      unireg_check= ((fld_type_modifier & AUTO_INCREMENT_FLAG) != 0 ?
                      Field::NEXT_NUMBER : // Automatic increment.
-        Field::NONE;
+                     Field::NONE);
   }
 
   decimals= fld_decimals ? (uint)atoi(fld_decimals) : 0;
@@ -9800,8 +9799,8 @@ key_map Field::get_possible_keys()
 
 void Field::set_explicit_default(Item *value)
 {
-  if (value && value->type() == Item::DEFAULT_VALUE_ITEM &&
+  if (value->type() == Item::DEFAULT_VALUE_ITEM &&
       !((Item_default_value*)value)->arg)
     return;
-  flags|= HAS_EXPLICIT_DEFAULT;
+  set_has_explicit_value();
 }

sql/field.h

@@ -342,6 +342,15 @@ public:
       unireg_check == TIMESTAMP_DNUN_FIELD;
   }
 
+  /*
+    Mark the field as having a value supplied by the client, thus it should
+    not be auto-updated.
+  */
+  void set_has_explicit_value()
+  {
+    flags|= HAS_EXPLICIT_VALUE;
+  }
+
   virtual void set_explicit_default(Item *value);
 
   /**

sql/sql_base.cc

@@ -8922,7 +8922,7 @@ fill_record_n_invoke_before_triggers(THD *thd, TABLE *table, List<Item> &fields,
     Re-calculate virtual fields to cater for cases when base columns are
     updated by the triggers.
   */
-  if (!result && triggers)
+  if (!result && triggers && table)
   {
     List_iterator_fast<Item> f(fields);
     Item *fld;
@@ -8932,9 +8932,12 @@ fill_record_n_invoke_before_triggers(THD *thd, TABLE *table, List<Item> &fields,
       fld= (Item_field*)f++;
       item_field= fld->filed_for_view_update();
       if (item_field && item_field->field && table && table->vfield)
+      {
+        DBUG_ASSERT(table == item_field->field->table);
         result= update_virtual_fields(thd, table, TRUE);
       }
     }
+  }
   return result;
 }
 
@@ -9064,6 +9067,7 @@ fill_record_n_invoke_before_triggers(THD *thd, TABLE *table, Field **ptr,
   */
   if (!result && triggers && *ptr)
   {
+    DBUG_ASSERT(table == (*ptr)->table);
     if (table->vfield)
       result= update_virtual_fields(thd, table, TRUE);
   }

sql/sql_base.h

@@ -304,7 +304,6 @@ TABLE *find_table_for_mdl_upgrade(THD *thd, const char *db,
 void mark_tmp_table_for_reuse(TABLE *table);
 bool check_if_table_exists(THD *thd, TABLE_LIST *table, bool *exists);
 int update_virtual_fields(THD *thd, TABLE *table, bool ignore_stored= FALSE);
-int update_default_fields(TABLE *table);
 int dynamic_column_error_message(enum_dyncol_func_result rc);
 
 extern TABLE *unused_tables;

sql/sql_insert.cc

@@ -2301,7 +2301,7 @@ end_create:
 TABLE *Delayed_insert::get_local_table(THD* client_thd)
 {
   my_ptrdiff_t adjust_ptrs;
-  Field **field,**org_field, *found_next_number_field, **dfield_ptr;
+  Field **field,**org_field, *found_next_number_field, **dfield_ptr= 0;
   TABLE *copy;
   TABLE_SHARE *share;
   uchar *bitmap;
@@ -2374,6 +2374,8 @@ TABLE *Delayed_insert::get_local_table(THD* client_thd)
   {
     copy->default_field= (Field**) client_thd->alloc((share->default_fields+1)*
                                                      sizeof(Field**));
+    if (!copy->default_field)
+      goto error;
     dfield_ptr= copy->default_field;
   }
   /*

sql/sql_load.cc

@@ -836,6 +836,10 @@ read_fixed_length(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
                             ER_WARN_TOO_FEW_RECORDS,
                             ER(ER_WARN_TOO_FEW_RECORDS),
                             thd->warning_info->current_row_for_warning());
+        /*
+          Timestamp fields that are NOT NULL are autoupdated if there is no
+          corresponding value in the data file.
+        */
         if (!field->maybe_null() && field->type() == FIELD_TYPE_TIMESTAMP)
           field->set_time();
       }
@@ -851,8 +855,9 @@ read_fixed_length(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
 	pos[length]=save_chr;
 	if ((pos+=length) > read_info.row_end)
 	  pos= read_info.row_end;	/* Fills rest with space */
-        field->set_explicit_default(NULL);
       }
+      /* Do not auto-update this field. */
+      field->set_has_explicit_value();
     }
     if (pos != read_info.row_end)
     {
@@ -982,15 +987,20 @@ read_sep_field(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
             DBUG_RETURN(1);
           }
           field->set_null();
-          field->set_explicit_default(NULL);
           if (!field->maybe_null())
           {
+            /*
+              Timestamp fields that are NOT NULL are autoupdated if there is no
+              corresponding value in the data file.
+            */
             if (field->type() == MYSQL_TYPE_TIMESTAMP)
               field->set_time();
             else if (field != table->next_number_field)
               field->set_warning(MYSQL_ERROR::WARN_LEVEL_WARN,
                                  ER_WARN_NULL_TO_NOTNULL, 1);
           }
+          /* Do not auto-update this field. */
+          field->set_has_explicit_value();
 	}
         else if (item->type() == Item::STRING_ITEM)
         {
@@ -1014,7 +1024,7 @@ read_sep_field(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
         if (field == table->next_number_field)
           table->auto_increment_field_not_null= TRUE;
         field->store((char*) pos, length, read_info.read_charset);
-        field->set_explicit_default(NULL);
+        field->set_has_explicit_value();
       }
       else if (item->type() == Item::STRING_ITEM)
       {
@@ -1057,6 +1067,7 @@ read_sep_field(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
           }
           if (!field->maybe_null() && field->type() == FIELD_TYPE_TIMESTAMP)
             field->set_time();
+          field->set_has_explicit_value();
           /*
             TODO: We probably should not throw warning for each field.
             But how about intention to always have the same number
@@ -1201,6 +1212,8 @@ read_xml_field(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
               field->set_warning(MYSQL_ERROR::WARN_LEVEL_WARN,
                                  ER_WARN_NULL_TO_NOTNULL, 1);
           }
+          /* Do not auto-update this field. */
+          field->set_has_explicit_value();
         }
         else
           ((Item_user_var_as_out_param *) item)->set_null_value(cs);
@@ -1215,7 +1228,7 @@ read_xml_field(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
         if (field == table->next_number_field)
           table->auto_increment_field_not_null= TRUE;
         field->store((char *) tag->value.ptr(), tag->value.length(), cs);
-        field->set_explicit_default(NULL);
+        field->set_has_explicit_value();
       }
       else
         ((Item_user_var_as_out_param *) item)->set_value(

sql/sql_update.cc

@@ -2158,7 +2158,7 @@ int multi_update::do_updates()
 	   copy_field_ptr++)
       {
 	(*copy_field_ptr->do_copy)(copy_field_ptr);
-        copy_field_ptr->to_field->set_explicit_default(NULL);
+        copy_field_ptr->to_field->set_has_explicit_value();
       }
 
       if (table->triggers &&

sql/table.cc

@@ -2473,9 +2473,7 @@ int open_table_from_share(THD *thd, TABLE_SHARE *share, const char *alias,
   /*
     Process virtual and default columns, if any.
   */
-  if (!share->vfields)
-    outparam->vfield= NULL;
-  else
+  if (share->vfields)
   {
     if (!(vfield_ptr = (Field **) alloc_root(&outparam->mem_root,
                                              (uint) ((share->vfields+1)*
@@ -2485,9 +2483,7 @@ int open_table_from_share(THD *thd, TABLE_SHARE *share, const char *alias,
     outparam->vfield= vfield_ptr;
   }
 
-  if (!share->default_fields)
-    outparam->default_field= NULL;
-  else
+  if (share->default_fields)
   {
     if (!(dfield_ptr = (Field **) alloc_root(&outparam->mem_root,
                                              (uint) ((share->default_fields+1)*
@@ -6546,7 +6542,7 @@ int TABLE::update_default_fields()
       If an explicit default value for a filed overrides the default,
       do not update the field with its automatic default value.
     */
-    if (!(dfield->flags & HAS_EXPLICIT_DEFAULT))
+    if (!(dfield->flags & HAS_EXPLICIT_VALUE))
     {
       if (sql_command_flags[cmd] & CF_INSERTS_DATA)
         res= dfield->evaluate_insert_default_function();
@@ -6556,7 +6552,7 @@ int TABLE::update_default_fields()
         DBUG_RETURN(res);
     }
     /* Unset the explicit default flag for the next record. */
-    dfield->flags&= ~HAS_EXPLICIT_DEFAULT;
+    dfield->flags&= ~HAS_EXPLICIT_VALUE;
   }
   DBUG_RETURN(res);
 }