buf_flush_try_neighbors(): Before invoking buf_page_t::ready_for_flush(),
check that the freshly looked up buf_pool.page_hash entry actually is
a buffer page and not a buf_pool.watch[] sentinel for purge buffering.

This race condition was introduced in MDEV-15053
(commit b1ab211d).
It is rather hard to hit this bug, because
buf_flush_check_neighbors() already checked the condition.
The problem exists if buf_pool.watch_set() was invoked for
a page in the range after the check in buf_flush_check_neighbor()
had been finished.

Thanks to Varun Gupta for suggesting this. This seems to
make main.innodb_ext_key,off more stable.

Invoking memcpy() on a NULL pointer is undefined behaviour
(even if the length is 0) and gives the compiler permission to
assume that the pointer is nonnull. Recent versions of GCC
(starting with version 8) are more aggressively optimizing away
checks for NULL pointers. This undefined behaviour would cause
a SIGSEGV in the test main.func_encrypt on an optimized debug build
on GCC 10.2.0.

Also, revert the work-around for the test that was attempted in
commit 85613a32.

This issue was caught by MemorySanitizer as well as on the
Microsoft Windows debug builds, thanks to /MD being used
starting with 10.4.

The code fix will also be applied to 10.2 because the regression
was introduced in commit afc9d00c.

Disable galera_var_replicate_myisam until fixed on 10.4

Corrects: 7803601d

This bug was already fixed in a previous commit.
Added test case from the MDEV to prove it's fixed.

For some reason, in the test main,innodb_ext_key,off
we frequently get unexpected EXPLAIN output, in particular
on Microsoft Windows debug builders. Let us comment out that
EXPLAIN statement for now.

Starting with commit ef3f71fa
MemorySanitizer would complain that we are writing uninitialized
data via the doublewrite buffer.

buf_dblwr_t::add_to_batch(): Zero out any unused part of the
doublewrite buffer, for PAGE_COMPRESSED and ROW_FORMAT=COMPRESSED
tables.

Reviewed by: Eugene Kosov

This prevents the clash between NOT_FIXED_DEC differing between server
and plugins if MYSQL_SERVER is not defined during plugin compilation.

It's a virtual method and it can't be inlined anyway. This allows type
plugins (mysql_json in particular) to use Type_handler_blob and / or
subclass it, without needing to explicitly expose the
vers_type_timestamp object.

Cleanup other linker errors

Additional case for PS protocol: UPDATE is converted to multi-update
in mysql_multi_update_prepare().

As part of MDEV-23855, we eliminated fil_system.LRU
and changed the way how InnoDB data files are opened.
We are also enforcing the innodb_open_files limit when new
data files are created.

The function fil_space_t::flush() would be invoked by
row_quiesce_table_start(). If the table was already in clean state,
it is possible that the data file is not open.

fil_space_t::flush_low(): If the data file is not open,
check with a debug assertion that there are no unflushed changes,
and carry on.

Reviewed by: Eugene Kosov and Thirunarayanan Balathandayuthapani

If and only if read_variable_length() returns true, the variable
blob_length will be uninitialized and not used. For some reason,
GCC 10.2.0 -Og debug builds would issue a warning.

An assertion inadvertently contained an assignment and an implicit
comparison to zero. The intention was to test equality.

Tighten access control - deny FILE_CREATE_PIPE_INSTANCE permission to
everyone except current user (the one that runs mysqld)

This patch solves two key problems.
1. There is a type number clash between MySQL and MariaDB. The number
   245, used for MariaDB Virtual Fields is the same as MySQL's JSON.
   This leads to corrupt FRM errors if unhandled. The code properly
   checks frm table version number and if it matches 5.7+ (until 10.0+)
   it will assume it is dealing with a MySQL table with the JSON
   datatype.
2. MySQL JSON datatype uses a proprietary format to pack JSON data. The
   patch introduces a datatype plugin which parses the format and convers
   it to its string representation.

The intended conversion path is to only use the JSON datatype within
ALTER TABLE <table> FORCE, to force a table recreate. This happens
during mysql_upgrade or via a direct ALTER TABLE <table> FORCE.

Convert the parameter to const as the function won't modify the pointer
value.

A wsrep transaction was started for EXECUTE IMMEDIATE, which
caused assertion failure when the executed statement was
CREATE TABLE which should be executed in TOI mode.

As a fix, don't start wsrep transaction for EXECUTE IMMEDIATE
to let the wsrep state logic to be handled from inside stored
procedure codepath.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

This avoids flushing file metadata on NTFS , and writing to <drive>:\$Log
file. With heavy write workload this can consume up to 1/3 of the
server's IO bandwidth.

Reviewed by : Marko

All relevant InnoDB changes from MySQL 5.7.32 have been applied
in preceding commits.

For a correlated subquery filesort is executed multiple times.
During each execution, sortlength() computed total sort key length in
Sort_keys::sort_length, without resetting it first.

Eventually Sort_keys::sort_length got larger than @@sort_buffer_size, which
caused filesort() to be aborted with error.

Fixed by making sortlength() to compute lengths only during the first
invocation. Subsequent invocations return pre-computed values.

Fix assertion `thd->in_active_multi_stmt_transaction() ||
thd->m_transaction_psi == __null' failed on MTR test
galera_sr.GCF-1051.

Add a new MTR test MDEV-23623 that reproduces the issue
deterministically and update wsrep-lib submodule, containing
the actual fix.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

Patch removes dict_index_t::stats_latch. Table/index statistics now
protected with dict_sys->mutex. That way statistics computation can
happen in parallel in several threads and dict_sys->mutex will be locked
only for a short period of time.

This patch is a joint work with Marko Mäkelä

dict_index_t::lock: make mutable which allows to pass const pointer
when only lock is touched in an object

btr_height_get()
btr_get_size(): make index argument const for better type safety

btr_estimate_number_of_different_key_vals(): now returns computed values
instead of setting fields in dict_index_t directly

remove everything related to dict_index_t::stats_latch

dict_stats_index_set_n_diff(): now returns computed values instead
of setting fields in dict_index_t directly

dict_stats_analyze_index():  now returns computed values instead
of setting fields in dict_index_t directly

Reviewed by: Marko Mäkelä