MDEV-28271 Assertion on TRUNCATE PARTITION for PARTITION BY SYSTEM_TIME

Like in MDEV-27217 vers_set_hist_part() for LIMIT depends on all
partitions selected in read_partitions. That bugfix just disabled
partition selection for DELETE with this check:

  if (table->pos_in_table_list &&
      table->pos_in_table_list->partition_names)
  {
    return HA_ERR_PARTITION_LIST;
  }

ALTER TABLE TRUNCATE PARTITION is a different story. First, it doesn't
update pos_in_table_list->partition_names, but
thd->lex->alter_info.partition_names. But we cannot depend on that
since alter_info will be stale for DML. Second, we should not disable
TRUNCATE PARTITION for that to be consistent with TRUNCATE TABLE
behavior.

Now we don't do vers_set_hist_part() for ALTER TABLE as this command
is not DML, so it does not produce history.

1 files changed, 1 insertions, 0 deletions

diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index b4bb3e7e61e..b1645a9c4a7 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -4034,6 +4034,7 @@ int ha_partition::external_lock(THD *thd, int lock_type)
          only for versioned DML. */
       thd->lex->sql_command != SQLCOM_SELECT &&
       thd->lex->sql_command != SQLCOM_INSERT_SELECT &&
+      thd->lex->sql_command != SQLCOM_ALTER_TABLE &&
       (error= m_part_info->vers_set_hist_part(thd)))
       goto err_handler;
   }