- Merge with 10.0-base

- Let Query Plan Footprint store join buffer type 
  in binary form, not string.
- Same for LooseScan type.

- If a subquery is correlated wrt a const table, it will change from
  being a "DEPENDENT SUBQUERY" into "SUBQUERY", at the end of its parent's 
  JOIN::optimize() call.  Handle this, update the subquery's QPF.
- Make show_explain.test to work
   = "Query plan already deleted" does not happen anymore.
   = Handle special case of queries that don't have top-level selects, like 
     SET x = (SELECT ...)

- Make query plan be re-saved after the first join execution
  (saving it after JOIN::cleanup is too late because EXPLAIN output 
   is currently produced before that)
- Handle QPF allocation/deallocation for edge cases, like unsuccessful
  BINLOG command.
- Work around the problem with UNION's direct subselects not being visible.
- Update test results ("Using temporary; Using filesort" are now always printed 
  last in the Extra column)
- This cset gets rid of memory leaks/crashes. Some result mismatches still remain.

- Update view.result (old EXPLAIN didn't match the execution)
- Put in a stub code to work around the 
  SELECT ... UNION SELECT ... ORDER BY (subuqery) problem

Based on James Briggs contribution.

INFORMATION_SCHEMA.LOCALES plugin.
Contribution by Roberto Spadim 

The test did RESET MASTER and then tried to use --sync_with_master
to wait for GTID-based replication to catch up. This though has
a race, there is a small window where the _old_ pre-RESET MASTER
position on the slave is higher than the new pos-RESET MASTER
position, causing the --sync_with_master to be a no-op.

Fix by using include/wait_condition.inc instead.

When we load the slave state from the mysql.gtid_slave_pos at server start, we
need to load all the rows into the in-memory hash, not just the most recent
one in each replication domain. Otherwise we accumulate cruft in the form of
old rows each time the server restarts.

- Support "using index for group-by (scanning) " queries

- Handle another specific case where there the JOIN 
  never had a query plan, but had multiple join->cleanup(full=true) calls
- The idea that there can only be MAX_TABLES subuqeries/unions was 
  wrong. Switch QPF_query to using a Dynamic_array.
  = make Dynamic_array template support size growth. its underlying
    DYNAMIC_ARRAY supports it. (this part will need more polishing)

In record_gtid(), too many rows were deleted from the slave position
hash - we need to always keep on to the most recent committed row,
so we have a valid slave position at all times.

- Handle statements inside SPs:
  = regular statements
  = SET command, which does not have its own statement.

- Handle execution of subquery from range optimizer: 
  allocate subquery QPFs on the same MEM_ROOT as the whole 
  query plan was allocated.

This requires that subselect's footprints are saved before it is deleted.

Attempt to save select's QPF exposes one to a variety of edge cases:
- the select may be a UNION's "fake select" which has no valid id
- optimization may fail in the middle (but subsequent JOIN::optimize() calls
  will succeed, despite the fact that there never was a query plan)

Single table UPDATE/DELETE
- Correctly print type=SIMPLE vs type=PRIMARY
- Handle UPDATE/DELETE of mergeable VIEWs: we get the 
  VIEW's select as the first subquery. 
  (MySQL 5.6 doesn't print it because it finds that the
   subquery is not attached to any select)

- Introduce back QueryPlan/QueryPlanFootprint separation for 
  single-table UPDATEs/DELETEs
- Create an empty QueryPlanFootprint for all kinds of queries

Fix wrong type for sub_id, which would cause overflow grief on
long-running server. Also some related renames for consistency.

- Make EXPLAIN UPDATE/DELETE use "Query Plan Footprints", too.

Part 2 of:
- Pass more tests
- select with subselects is now shown with type=PRIMARY where it used to be (incorrectly) 'SIMPLE' 

- Pass more tests
- select with subselects is now shown with type=PRIMARY where it used to be (incorrectly) 'SIMPLE' 

- Fix more problems to pass the testsuite (not finished yet)

- Add further details, the goal is to pass the testsuite
- SJM-nests are not printed correctly yet.

- Introduce "Query Plan Footprints" (abbrev. QPFs)
  QPF is a part of query plan that is 
  1. sufficient to produce EXPLAIN output,
  2. can be used to produce EXPLAIN output even after its subquery/union
     was executed and deleted
  3. is cheap to save so that we can always save query plans

- This patch doesn't fully address #2, we make/save strings for 
  a number of EXPLAIN's columns.  This will be fixed.

Implement discovery of table non-existence, and related changes:

1. Split GTS_FORCE_DISCOVERY (that was meaning two different things in
two different functions) into GTS_FORCE_DISCOVERY and GTS_USE_DISCOVERY.
2. Move GTS_FORCE_DISCOVERY implementation into open_table_def().
3. In recover_from_failed_open() clear old errors *before* discovery,
not after successful discovery. The final error should come
from the discovery.
4. On forced discovery delete table .frm first. Discovery will write
a new one, if desired.
5. If the frm file exists, but not the table in the engine, force
rediscovery if the engine supports it.

mark the SEQUENCE engine as both SBR and RBR capable :)

implement a non-dummy discover_table_existence() method

1. default db type for partitions was stored as 1-byte DB_TYPE code,
   which doesn't work for dynamically generated codes.
2. storage engine plugin for default db type wasn't locked at all,
   which could trivially crash for dynamic plugins.

Now the storage engine name is stored in the extra2 section,
and the plugin is correctly locked.

Remove few ifdef's

1. DROP DATABASE should use ha_discover_table_names(), not look at .frm files.
2. filename_to_tablename() also encodes temp file names #sql- -> #mysql50##sql
3. no special treatment for #sql- files, no TABLE_LIST::internal_tmp_table
4. discover also table file names, that start from #

Minor modification to trigger buildbot.