MDEV-10139 Support for SEQUENCE objects

- SETVAL(sequence_name, next_value, is_used, round)
- ALTER SEQUENCE, including RESTART WITH

Other things:
- Added handler::extra() option HA_EXTRA_PREPARE_FOR_ALTER_TABLE to signal
  ha_sequence() that it should allow write_row statments.
- ALTER ONLINE TABLE now works with SEQUENCE:s

1 files changed, 20 insertions, 1 deletions

diff --git a/sql/ha_sequence.cc b/sql/ha_sequence.cc
index 5ff5a4eb213..a918da92be2 100644
--- a/sql/ha_sequence.cc
+++ b/sql/ha_sequence.cc
@@ -201,7 +201,7 @@ int ha_sequence::write_row(uchar *buf)
 
   /*
     User tries to write a row
-    - Check that row is an accurate object
+    - Check that the new row is an accurate object
     - Update the first row in the table
   */
 
@@ -290,6 +290,25 @@ int ha_sequence::info(uint flag)
   DBUG_RETURN(false);
 }
 
+
+int ha_sequence::extra(enum ha_extra_function operation)
+{
+  if (operation == HA_EXTRA_PREPARE_FOR_ALTER_TABLE)
+  {
+    /* In case of ALTER TABLE allow ::write_row() to copy rows */
+    sequence->initialized= SEQUENCE::SEQ_IN_PREPARE;
+  }
+  return file->extra(operation);
+}
+
+bool ha_sequence::check_if_incompatible_data(HA_CREATE_INFO *create_info,
+                                             uint table_changes)
+{
+  /* Table definition is locked for SEQUENCE tables */
+  return(COMPATIBLE_DATA_YES);
+}
+
+
 int ha_sequence::external_lock(THD *thd, int lock_type)
 {
   int error= file->external_lock(thd, lock_type);