- Handle the case when EXPLAIN UPDATE/DELETE has pruned away all partitions.

- Address review feedback: more renames

- Address review feedback: rename files

- Address review feedback: rename nearly any name used by the new EXPLAIN code.

- Added a testcase

- Make EXPLAIN {PARTITIONS,EXTENDED} {UPDATE,DELETE} work.

- Make EXPLAIN UPDATE/DELETE work inside SPs
- Return correct error code from mysql_delete()
- EXPLAIN <multi-DELETE> will create a multi_delete object (as it 
  affects the optimization). select_result will be only used for 
  producing EXPLAIN output.

- Query plan footprint (in new terms, "EXPLAIN structure") should always keep 
  a copy of key_name.  This is because the table might be a temporary table which
  may be already freed by the time we use query plan footprint.

- If we're running explain with flags, use the same set of flags to make EXPLAIN columns 
  and contents.

- Add EXPLAIN output print out for INSERT/REPLACE ... SELECT

- update mysqld--help.result

- Don't forget to delete the query plan footprint when 
  the query wasn't printed into slow query log for some reason
- ALso removed some garbage code.

- Don't print a plan when the statement didn't produce it
- Also, add first testcase. We can't check the EXPLAIN from the slow log itself, though.

- Initial implementation. 

- Make QPF structures store data members, not strings. 
  This is not fully possible, because table names (and hence 
  key names, etc) can be deleted, and we have to store strings.

- Post-merge fixes (conflict with DELETE .. RETURNING)
- Add a testcase with EXPLAIN ... DELETE ... RETURNING

- Merge with current 10.0-base

- Merge with current 10.0-base

Implement @@gtid_binlog_state. This is the internal state of the binlog
(most recent GTID logged for every domain_id and server_id). This allows
to save the state before RESET MASTER and restore it afterwards.

The ignored events are not written to the relay log, but instead a fake
Rotate event is generated to handle update of position.

Extend this for Gtid so we similarly generate a fake Gtid_list event
to update the GTID position.

Also fix an unrelated test issue that got triggered by the added test cases.

- Let sp_get_flags_for_command() set sp_head::MULTI_RESULTS for DELETE ... RETURNING, 
  like it does for all statements that return a resultset.

  
Currently the loose scan code in opt_range.cc considers all indexes as
possible for the access method. Due to inexact statistics it may happen
that a loose scan is selected over a unique index.
  
This is clearly wrong since a "loose scan" over a unique index will read
the same keys as a direct index scan, but the loose scan has more overhead.
  
This task adds a rule to skip unique indexes for loose scan.

It was fixed as merge changes for MDEV-4811.

bMDEV-4906: When event apply fails, next SQL thread start errorneously commits the failing GTID to gtid_slave_pos

When a GTID event is executed, we remember the contained GTID position so that
when we have applied the entire event group we can commit it to
gtid_slave_pos.

However, if the event group fails to apply due to some error and the SQL
thread aborts, the code did not correctly clear the remembered GTID. Thus,
when SQL thread was restarted, the old GTID of the failing event group was
incorrectly updated to gtid_slave_pos when the initial rotate event was
executed, corrupting the GTID position.

mysql-test/r/func_set.result:
  merge

The function SELECT_LEX::mark_const_derived() must take into account that
in DELETE ... RETURNING join == NULL.

MDEV-4820: Empty master does not give error for slave GTID position that does not exist in the binlog

The main bug here was the following situation:

Suppose we set up a completely new master2 as an extra multi-master to an
existing slave that already has a different master1 for domain_id=0. When the
slave tries to connect to master2, master2 will not have anything that slave
requests in domain_id=0, but that is fine as master2 is supposedly meant to
serve eg. domain_id=1. (This is MDEV-4485).

But suppose that master2 then actually starts sending events from
domain_id=0. In this case, the fix for MDEV-4485 was incomplete, and the code
would fail to give the error that the position requested by the slave in
domain_id=0 was missing from the binlogs of master2. This could lead to lost
events or completely wrong replication.

The patch for this bug fixes this issue.

In addition, it cleans up the code a bit, getting rid of the fake_gtid_hash in
the code. And the error message when slave and master have diverged due to
alternate future is clarified, as requested in the bug description.

modified:
  mysql-test/r/dyncol.result
  mysql-test/r/type_time.result
  mysql-test/t/dyncol.test
  mysql-test/t/type_time.test
  mysys/ma_dyncol.c
  sql/item.cc
  sql/item_func.cc
pending merges:
  Alexander Barkov 2013-08-12 MDEV-4652 Wrong result for CONCAT(GREATEST(T...
    sanja@montyprogr... 2013-08-01 MDEV-4811 Assertion `offset < 0x1f' f...

set num_flag[] unconditionally, not under "if (column_names)"

http://ronaldbradford.com/blog/unexplained-trivial-mysql-behavior-2013-08-02/