Problem:
========
  During buffer pool resizing, InnoDB recreates the dictionary hash
tables. Dictionary hash table reuses the heap of AHI hash tables.
It leads to memory corruption.

Fix:
====
- While disabling AHI, free the heap and AHI hash tables. Recreate the
AHI hash tables and assign new heap when AHI is enabled.

- btr_blob_free() access invalid page if page was reallocated during
buffer poolresizing. So btr_blob_free() should get the page from
buf_pool instead of using existing block.

- btr_search_enabled and block->index should be checked after
acquiring the btr_search_sys latch

- Moved the buffer_pool_scan debug sync to earlier before accessing the
btr_search_sys latches to avoid the hang of truncate_purge_debug
test case

- srv_printf_innodb_monitor() should acquire btr_search_sys latches
before AHI hash tables.

srv_purge_should_exit(): Report progress on slow shutdown
not only to systemd, but also to the error log.

Problem:
=======
  While evicting the uncompressed page from buffer pool, InnoDB writes
the checksum for the compressed page in buf_LRU_free_page().
So while flushing the compressed page, checksum validation fails
when innodb_checksum_algorithm variable changed to strict_none.

Solution:
========
- Calculate the checksum only during flushing of page. Removed the
checksum write in buf_LRU_free_page().

Compare to trx_roll_crash_recv_trx directly where needed.

innobase_init(): On every path to refused startup, log the reason
to refuse startup as an error, instead of a note.

Part of MDEV-19061 - table_share used for reading statistical tables is
                     not protected

Previously multiple threads were allowed to load histograms concurrently.
There were no known problems caused by this. But given amount of data
races in this code, it'd happen sooner or later.

To avoid scalability bottleneck, histograms loading is protected by
per-TABLE_SHARE atomic variable.

Whenever histograms were loaded by preceding statement (hot-path), a
scalable load-acquire check is performed.

Whenever histograms have to be loaded anew, mutual exclusion for loaders
is established by atomic variable. If histograms are being loaded
concurrently, statement waits until load is completed.

- Table_statistics::total_hist_size moved to TABLE_STATISTICS_CB: only
  meaningful within TABLE_SHARE (not used for collected stats).
- TABLE_STATISTICS_CB::histograms_can_be_read and
  TABLE_STATISTICS_CB::histograms_are_read are replaced with a tri state
  atomic variable.
- Simplified away alloc_histograms_for_table_share().

Note: there's still likely a data race if a thread attempts accessing
histograms data after it failed to load it (because of concurrent load).
It was there previously and goes out of the scope of this effort. One way
of fixing it could be reviving TABLE::histograms_are_read and adding
appropriate checks whenever it is needed.

Part of MDEV-19061 - table_share used for reading statistical tables is
                     not protected

Previously multiple threads were allowed to load statistics concurrently.
There were no known problems caused by this. But given amount of data
races in this code, it'd happen sooner or later.

To avoid scalability bottleneck, statistics loading is protected by
per-TABLE_SHARE atomic variable.

Whenever statistics were loaded by preceding statement (hot-path), a
scalable load-acquire check is performed.

Whenever statistics have to be loaded anew, mutual exclusion for loaders
is established by atomic variable. If statistics are being loaded
concurrently, statement waits until load is completed.

TABLE_STATISTICS_CB::stats_can_be_read and
TABLE_STATISTICS_CB::stats_is_read are replaced with a tri state atomic
variable.

Part of MDEV-19061 - table_share used for reading statistical tables is
                     not protected

Removed redundant loops, integrated logics into the caller instead.
Unified condition in read_statistics_for_tables(), less
"table_share != NULL" checks, no more potential "table_share == NULL"
dereferencing.

Part of MDEV-19061 - table_share used for reading statistical tables is
                     not protected

MDEV-22744 *SAN: sql/item_xmlfunc.cc:791:43: runtime error: downcast of address ... which does not point to an object of type 'Item_func' note: object is of type 'Item_bool' (on optimized builds)

In Item_nodeset_func_predicate::val_nodeset, args[1] is not necessarily
an Item_func descendant. It can be Item_bool.

Removing a wrong cast. It was not really needed anyway.

when checking for free port, use the same logic (IPv6 socket address
/ dual socket), like the server would.

Previous solution for testing whether port is free was trying to bind
IPv4 socket on INADDR_ANY.

This not work now on some reason, that attempt succeeds, even if there is
an existing IPv6-dual socket listening on 0.0.0.0:3306

It works, but irritates people who look into the log and see
traces of 32bit custom action server.

Pre-definitions are allowed for non-embedded.
Failur catched with:
```
cmake ../../10.1 -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER=g++-9
-DCMAKE_C_COMPILER=gcc-9 -DWITH_EMBEDDED_SERVER=ON -DCMAKE_BUILD_TYPE=Debug
-DPLUGIN_{ARCHIVE,TOKUDB,MROONGA,OQGRAPH,ROCKSDB,PERFSCHEMA,SPIDER,SPHINX}=N
-DMYSQL_MAINTAINER_MODE=ON -DNOT_FOR_DISTRIBUTION=ON
```
Alternative fix would be
```
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -201,8 +201,10 @@ LEX_STRING current_user= { C_STRING_WITH_LEN("*current_user") };
 LEX_STRING current_role= { C_STRING_WITH_LEN("*current_role") };
 LEX_STRING current_user_and_current_role= { C_STRING_WITH_LEN("*current_user_and_current_role") };

+#ifndef EMBEDDED_LIBRARY
 class ACL_USER;
 static ACL_USER *find_user_or_anon(const char *host, const char *user, const char *ip);
+#endif
```

- `SET DEFAULT ROLE xxx [FOR yyy]` should say:
  "User yyy has not been granted a role xxx" if:
    - The current user (not the user `yyy` in the FOR clause) can see the
    role xxx. It can see the role if:
      * role exists in `mysql.roles_mappings` (traverse the graph),
      * If the current user has read access on `mysql.user` table - in
    that case, it can see all roles, granted or not.
    - Otherwise it should be "Invalid role specification".

In other words, it should not be possible to use `SET DEFAULT ROLE` to discover whether a specific role exist or not.

otherwise it reaches "0 tests left" state and then waits for
a few minutes  for all workers to complete their tests.

show failures. account for retries.

don't fetch the complete history of all submodules, it's rarely needed

Revert "MDEV-12445 : Rocksdb does not shutdown worker threads and aborts in memleak check on server shutdown"

This reverts commit 6f1f9114.

because it doesn't do anything now (the server doesn't check
my_disable_leak_check) and it never did anything before
(because without `extern` it simply created a local instance of
my_disable_leak_check, did not affect server's my_disable_leak_check).

WITH_ROCKSDB_ZSTD must use the same capitalization as
in the foreach loop

MDEV-21958 Query having many NOT-IN clauses running forever and causing available free memory to use completely

let thd->killed to abort range optimizer

cannot use the current THD::mem_root, because it can be temporarily
reassigned to something with a very different life time
(e.g. to TABLE::mem_root or range optimizer mem_root).

the existing ".git/" rule only filters out .git directories,
but as we have submodules now, we have to filter out .git files too.

data_file_length == 0 in mi_repair() is normal for REPAIR ... USE_FRM.
But in-file links (for blocks and deleted chain) must be compared with
the real file length to avoid spurious "link points outside datafile"
warnings and arbitrary block skipping.

The build was broken on CentOS 5 and CentOS 6 as a result of
commit 18d8f06f introducing
some constructs that old GCC versions could not cope with.

The build was broken in the parent
commit 18d8f06f.

namespace intrusive: removed

split class into two: ilist<T> and sized_ilist<T> which has a size field.

ilist<T> no more NULLify pointers to bring a slignly better performance.
As a consequence, fil_space_t::is_in_unflushed_spaces and
fil_space_t::is_in_rotation_list boolean members are needed now.

MDEV-20578 Got error 126 when executing undo undo_key_delete
upon Aria crash recovery

The crash happens in this scenario:
- Table with unique keys and non unique keys
- Batch insert (LOAD DATA or INSERT ... SELECT) with REPLACE
- Some insert succeeds followed by duplicate key error

In the above scenario the table gets corrupted.

The bug was that we don't generate any undo entry for the
failed insert as the whole insert can be ignored by undo.
The code did however not take into account that when bulk
insert is used, we would write cached keys to the file on
failure and undo would wrongly ignore these.

Fixed by moving the writing of the cache keys after we write
the aborted-insert event to the log.