- Switch Explain data structure from "flat" representation of
  SJ-Materialization into nested one.
- Update functions that print tabular output to operate on the
  nested structure.
- Add function to generate JSON output.

- Print r_loops
- Always print r_* members. Print NULL values if no scans took place
- Added testcases.

- Basic support for JOIN buffering
- The output is not polished but catches the main point:
  tab->select_cond and tab->cache_select->cond are printed separately.
- Hash join support is poor still.

- Also fixed identation in JOIN_TAB::save_explain_data

Writing JSON:
- Fix a bug in Single_line_formatting_helper
- Add Json_writer_nesting_guard - safety class

EXPLAIN JSON support
- Add basic subquery support
- Add tests for UNION/UNION ALL.

Problem was that test tried to calculate number of pages on
buffer pool and operations done to them. This is not realible
way on buildbot.

Problem is that there is additional error message from function
that is not really needed now.

  Problem is that test could open Microsoft C++ Client Debugger
  windows with abort exceptin. Lets not try to test this on
  windows.

innodb.innodb_stats_drop_locked fail and
innodb.innodb_stats_fetch_nonexistent fails in buildbot on Windows

Analysis: Problem is that innodb_stats_create_on_corrupted
test renames mysql.innodb.index_stats and all the rest
are dependend on this table.

Fix: After rename back to original, restart mysqld to
make sure that table is correct.

Analysis: Test case uses Linux specific error codes.

Fix: Can't run test case with Windows currently because requires
to inject error to system.

        test results updated with the new GIS-related IS tables.

Analysis: If innodb_use_trim is not enabled or system does not
support fallocate to make persistent trim, we should always
write full page not only partial pages.

Fix for embedded build failure.
Also added wsrep_info plugin library to server debian package.

wsrep_info INFORMATION_SCHEMA plugin to provide WSREP_STATUS
and WSREP_MEMBERSHIP tables.

- Drop all tables in explain_json.test
- Tabular form should print ref='' when type='fulltext' (another peculiarity
  of the traditional EXPLAIN format)
- String_list::append_str should allocate memory for \0, too
- Some temporary code for EXPLAIN JSON and join buffering.

MDEV-7146 NULLIF returns unexpected result with a YEAR field

Problem is that page compressed tables currently require atomic_blobs and
that feature is not availabe currently for row_format=redundant.

Fix: Disallow page compressed create option if table row_format=redundant.

Merge Facebook commit https://github.com/facebook/mysql-5.6/commit/cd063ab930f05efdba39d504543998512d1bd71f
authored by Peng Tian from https://github.com/facebook/mysql-5.6

Introduced a new configuration variable innodb_fatal_semaphore_wait_threshold,
it makes the fatal semaphore timeout configurable. Modified original commit
so that no MariaDB server files are changed, instead introduced a new
InnoDB/XtraDB configuration variable.

Its default/min/max vlaues are 600/1/2^32-1 in seconds (it was hardcoded
as 600, now its default value is 600, so the default behavior of this diff
should be no change).

Analysis: Status variables were missing from innodb_status_variables
array.

Fix: Add missing status variables to the array.

Merged Facebook commit 617aef9f911d825e9053f3d611d0389e02031225
authored by Inaam Rana to InnoDB storage engine (not XtraDB)
from https://github.com/facebook/mysql-5.6

WL#7047 - Optimize buffer pool list scans and related batch processing

Reduce excessive scanning of pages when doing flush list batches. The
fix is to introduce the concept of "Hazard Pointer", this reduces the
time complexity of the scan from O(n*n) to O.

The concept of hazard pointer is reversed in this work. Academically
hazard pointer is a pointer that the thread working on it will declar
such and as long as that thread is not done no other thread is allowe
do anything with it.

In this WL we declare the pointer as a hazard pointer and then if any
thread attempts to work on it, it is allowed to do so but it has to a
the hazard pointer to the next valid value. We use hazard pointer sol
reverse traversal of lists within a buffer pool instance.

Add an event to control the background flush thread. The background f
thread wait has been converted to an os event timed wait so that it c
signalled by threads that want to kick start a background flush when
buffer pool is running low on free/dirty pages.

(forgot to do "git add" for two files in the previous commit for MDEV-5528)

we do not return simulated out of file space on read operation,
that would cause crash.

Merging from 10.0 (pre-requisite for  MDEV-5528)

Merge Facebook commit 154c579b828a60722a7d9477fc61868c07453d08
and e8f0052f9b112dc786bf9b957ed5b16a5749f7fd authored
by Steaphan Greene from https://github.com/facebook/mysql-5.6

Optimize prefix index queries to skip cluster index lookup when possible.

Currently InnoDB will always fetch the clustered index (primary key
index) for all prefix columns in an index, even when the value of a
particular record is smaller than the prefix length. This change
optimizes that case to use the record from the secondary index and avoid
the extra lookup.

Also adds two status vars that track how effective this is:

innodb_secondary_index_triggered_cluster_reads:
Times secondary index lookup triggered cluster lookup.

innodb_secondary_index_triggered_cluster_reads_avoided:
Times prefix optimization avoided triggering cluster lookup.

Use fn_ext2() to get the file extension from last occurrence
of FN_EXTCHAR ('.') instead.