Reintroduces delete_while_scanning optimization for multi_delete.
Reverse some test changes from the initial feature devlopment now
that we delete-on-the-fly once again.
We now allow multitable queries with order by and limit, such as:
delete t1.*, t2.* from t1, t2 order by t1.id desc limit 3;
To predict what rows will be deleted, run the equivalent select:
select t1.*, t2.* from t1, t2 order by t1.id desc limit 3;
Additionally, index hints are now supported with single table delete statements:
delete from t2 use index(xid) order by (id) limit 2;
This approach changes the multi_delete SELECT result interceptor to use a temporary
table to collect row ids pertaining to the rows that will be deleted, rather than
directly deleting rows from the target table(s). Row ids are collected during
send_data, then read during send_eof to delete target rows. In the event that the
temporary table created in memory is not big enough for all matching rows, it is
converted to an aria table.
Other changes:
- Deleting from a sequence now affects zero rows instead of emitting an error
Limitations:
- The federated connector does not create implicit row ids, so we to use a key
when conditionally deleting. See the change in federated_maybe_16324629.test
- FLUSH GLOBAL STATUS now resets most global_status_vars.
At this stage, this is mainly to be used for testing.
- FLUSH SESSION STATUS added as an alias for FLUSH STATUS.
- FLUSH STATUS does not require any privilege (before required RELOAD).
- FLUSH GLOBAL STATUS requires RELOAD privilege.
- All global status reset moved to FLUSH GLOBAL STATUS.
- Replication semisync status variables are now reset by
FLUSH GLOBAL STATUS.
- In test cases, the only changes are:
- Replace FLUSH STATUS with FLUSH GLOBAL STATUS
- Replace FLUSH STATUS with FLUSH STATUS; FLUSH GLOBAL STATUS.
This was only done in a few tests where the test was using SHOW STATUS
for both local and global variables.
- Uptime_since_flush_status is now always provided, independent if
ENABLED_PROFILING is enabled when compiling MariaDB.
- @@global.Uptime_since_flush_status is reset on FLUSH GLOBAL STATUS
and @@session.Uptime_since_flush_status is reset on FLUSH SESSION STATUS.
- When connected, @@session.Uptime_since_flush_status is set to 0.
