using "show variables", rather than take the value from my.cnf.

"show variables" is more accurate than my.cnf,it also works for parameters
set on the mysqld command line, which is especially important for MTR.

MDEV-12975 InnoDB redo log minimum size check uses detected file size instead of requested innodb_log_file_size

log_calc_max_ages(): Use the requested size in the check, instead of
the detected redo log size. The redo log will be resized at startup
if it differs from what has been requested.

MDEV-12975 InnoDB redo log minimum size check uses detected file size instead of requested innodb_log_file_size

log_calc_max_ages(): Use the requested size in the check, instead of
the detected redo log size. The redo log will be resized at startup
if it differs from what has been requested.

The bug happens because of a combination of unfortunate circumstances:

1. Arguments args[0] and args[2] of Item_func_concat point recursively
(through Item_direct_view_ref's) to the same Item_func_conv_charset.
Both args[0]->args[0]->ref[0] and args[2]->args[0]->ref[0] refer to
this Item_func_conv_charset.

2. When Item_func_concat::args[0]->val_str() is called,
Item_func_conv_charset::val_str() writes its result to
Item_func_conc_charset::tmp_value.

3. Then, for optimization purposes (to avoid copying),
Item_func_substr::val_str() initializes Item_func_substr::tmp_value
to point to the buffer fragment owned by Item_func_conv_charset::tmp_value
Item_func_substr::tmp_value is returned as a result of
Item_func_concat::args[0]->val_str().

4. Due to optimization to avoid memory reallocs,
Item_func_concat::val_str() remembers the result of args[0]->val_str()
in "res" and further uses "res" to collect the return value.

5. When Item_func_concat::args[2]->val_str() is called,
Item_func_conv_charset::tmp_value gets overwritten (see #1),
which effectively overwrites args[0]'s Item_func_substr::tmp_value (see #3),
which effectively overwrites "res" (see #4).

This patch does the following:

a. Changes Item_func_conv_charset::val_str(String *str) to use
   tmp_value and str the other way around. After this change tmp_value
   is used to store a temporary result, while str is used to return the value.
   The fixes the second problem (without SUBSTR):
     SELECT CONCAT(t2,'-',t2) c2
       FROM (SELECT CONVERT(t USING latin1) t2 FROM t1) sub;
   As Item_func_concat::val_str() supplies two different buffers when calling
   args[0]->val_str() and args[2]->val_str(), in the new reduction the result
   created during args[0]->val_str() does not get overwritten by
   args[2]->val_str().

b. Fixing the same problem in val_str() for similar classes

   Item_func_to_base64
   Item_func_from_base64
   Item_func_weight_string
   Item_func_hex
   Item_func_unhex
   Item_func_quote
   Item_func_compress
   Item_func_uncompress
   Item_func_des_encrypt
   Item_func_des_decrypt
   Item_func_conv_charset
   Item_func_reverse
   Item_func_soundex
   Item_func_aes_encrypt
   Item_func_aes_decrypt
   Item_func_buffer

c. Fixing Item_func::val_str_from_val_str_ascii() the same way.
   Now Item_str_ascii_func::ascii_buff is used for temporary value,
   while the parameter passed to val_str() is used to return the result.
   This fixes the same problem when conversion (from ASCII to e.g. UCS2)
   takes place. See the ctype_ucs.test for example queries that returned
   wrong results before the fix.

d. Some Item_func descendand classes had temporary String buffers
   (tmp_value and tmp_str), but did not really use them.
   Removing these temporary buffers from:

   Item_func_decode_histogram
   Item_func_format
   Item_func_binlog_gtid_pos
   Item_func_spatial_collection:

e. Removing Item_func_buffer::tmp_value, because it's not used any more.

f. Renaming Item_func_[un]compress::buffer to "tmp_value",
   for consistency with other classes.

Note, this patch does not fix the following classes
(although they have a similar problem):

   Item_str_conv
   Item_func_make_set
   Item_char_typecast

They have a complex implementations and simple swapping between "tmp_value"
and "str" won't work. These classes will be fixed separately.

The option was basically duplicating InnoDB functionality.
Persistent statistics can be accessed via the tables
mysql.innodb_table_stats and mysql.innodb_index_stats.

These functions cannot possibly work in MariaDB 10.2, and it is
uncertain if they really work in 10.1 either.

This has been implemented in for cmake-3.6 to match distro version
of what the filename should look like.

Thanks to Domen Vranka for the suggestion.

regex didn't replace lines that were split by 16K chunk reads.

             lock not released after timeout

Release GRL if FLUSH TABLES phase failed.

The problem lies in how CURRENT_ROLE is defined. The
Item_func_current_role inherits from Item_func_sysconst, which defines
a safe_charset_converter to be a const_charset_converter.

During view creation, if there is no role previously set, the current_role()
function returns NULL.

This is captured on item instantiation and the
const_charset_converter call subsequently returns an Item_null.
In turn, the function is replaced with Item_null and the view is
then created with an Item_null instead of Item_func_current_role.

Without this patch, the first SHOW CREATE VIEW from the testcase would
have a where clause of WHERE role_name = NULL, while the second SHOW
CREATE VIEW would show a correctly created view.

The same applies for the DATABASE function, as it can change as well.

There is an additional problem with CURRENT_ROLE() when used in a
prepared statement. During prepared statement creation we used to set
the string_value of the function to the current role as well as the
null_value flag. During execution, if CURRENT_ROLE was not null, the
null_value flag was never set to not-null during fix_fields.

Item_func_current_user however can never be NULL so it did not show this
problem in a view before. At the same time, the CURRENT_USER() can not
be changed between prepared statement execution and creation so the
implementation where the value is stored during fix_fields is
sufficient.

Note also that DATABASE() function behaves differently during prepared
statements. See bug 25843 for details or commit
7e0ad09e

The problem lies in not checking role privileges as well during SHOW
DATABASES command. This problem is also apparent for SHOW CREATE
DATABASE command.

Other SHOW COMMANDS make use of check_access, which in turn makes use of
acl_get for both priv_user and priv_role parts, which allows them to
function correctly.

dict_table_t::thd: Remove. This was only used by btr_root_block_get()
for reporting decryption failures, and it was only assigned by
ha_innobase::open(), and never cleared. This could mean that if a
connection is closed, the pointer would become stale, and the server
could crash while trying to report the error. It could also mean
that an error is being reported to the wrong client. It is better
to use current_thd in this case, even though it could mean that if
the code is invoked from an InnoDB background operation, there would
be no connection to which to send the error message.

Remove dict_table_t::crypt_data and dict_table_t::page_0_read.
These fields were never read.

fil_open_single_table_tablespace(): Remove the parameter "table".

MDEV-13063 Server crashes in intern_plugin_lock or assertion `plugin_ptr->ref_count == 1' fails in plugin_init

if a forced plugin is disabled (for any reason, e.g. invalid command-line
option) - it's an error

Cover innodb.table_flags with the new innodb_page_size.combinations
32k and 64k.

dict_sys_tables_type_validate(): Remove an assertion that made a
check in the function redundant. Remove the excessive output to
the error log, as the invalid SYS_TABLES.TYPE value is already being
output.

Add a missing #include "sync0types.h" that was removed in MDEV-12674.

Add a test case for corrupting SYS_TABLES.TYPE,
and for ROW_FORMAT=REDUNDANT, the unused field SYS_TABLES.MIX_LEN
that must be ignored (InnoDB before MySQL 5.5 wrote uninitialized
garbage to this column).

MariaDB 10.0 appears to validate the SYS_TABLES.TYPE properly.
This is a test-only change.

in innodb_read_only mode.

The reason for the hang is that there was no notification received about
completed read io. File handles are bound to completion_port, and there
were no background "write" threads that would be waiting on completion_port,
only 2 "read" threads waiting on read_completion_port were active.

The fix is to use a single IO completion port for all IOs, if
innodb_read_only is set.

fil_crypt_read_crypt_data(): Remove an unnecessary
acquisition of fil_system->mutex. Remove a duplicated condition
from the callers.

When the server is started in innodb_read_only mode, there cannot be
any writes to persistent InnoDB/XtraDB files. Just like the creation
of buf_flush_page_cleaner_thread is skipped in this case, also
the creation of the XtraDB-specific buf_flush_lru_manager_thread
should be skipped.

When a slow shutdown is performed soon after spawning some work for
background threads that can create or commit transactions, it is possible
that new transactions are started or committed after the purge has finished.
This is violating the specification of innodb_fast_shutdown=0, namely that
the purge must be completed. (None of the history of the recent transactions
would be purged.)

Also, it is possible that the purge threads would exit in slow shutdown
while there exist active transactions, such as recovered incomplete
transactions that are being rolled back. Thus, the slow shutdown could
fail to purge some undo log that becomes purgeable after the transaction
commit or rollback.

srv_undo_sources: A flag that indicates if undo log can be generated
or the persistent, whether by background threads or by user SQL.
Even when this flag is clear, active transactions that already exist
in the system may be committed or rolled back.

innodb_shutdown(): Renamed from innobase_shutdown_for_mysql().
Do not return an error code; the operation never fails.
Clear the srv_undo_sources flag, and also ensure that the background
DROP TABLE queue is empty.

srv_purge_should_exit(): Do not allow the purge to exit if
srv_undo_sources are active or the background DROP TABLE queue is not
empty, or in slow shutdown, if any active transactions exist
(and are being rolled back).

srv_purge_coordinator_thread(): Remove some previous workarounds
for this bug.

innobase_start_or_create_for_mysql(): Set buf_page_cleaner_is_active
and srv_dict_stats_thread_active directly. Set srv_undo_sources before
starting the purge subsystem, to prevent immediate shutdown of the purge.
Create dict_stats_thread and fts_optimize_thread immediately
after setting srv_undo_sources, so that shutdown can use this flag to
determine if these subsystems were started.

dict_stats_shutdown(): Shut down dict_stats_thread. Backported from 10.2.

srv_shutdown_table_bg_threads(): Remove (unused).

Problem appears to be that the function fsp_flags_try_adjust()
is being unconditionally invoked on every .ibd file on startup.
Based on performance investigation also the top function
fsp_header_get_crypt_offset() needs to addressed.

Ported implementation of fsp_header_get_encryption_offset()
function from 10.2 to fsp_header_get_crypt_offset().

Introduced a new function fil_crypt_read_crypt_data()
to read page 0 if it is not yet read.

fil_crypt_find_space_to_rotate(): Now that page 0 for every .ibd
file is not read on startup we need to check has page 0 read
from space that we investigate for key rotation, if it is not read
we read it.

fil_space_crypt_get_status(): Now that page 0 for every .ibd
file is not read on startup here also we need to read page 0
if it is not yet read it. This is needed
as tests use IS query to wait until background encryption
or decryption has finished and this function is used to
produce results.

fil_crypt_thread(): Add is_stopping condition for tablespace
so that we do not rotate pages if usage of tablespace should
be stopped. This was needed for failure seen on regression
testing.

fil_space_create: Remove page_0_crypt_read and extra
unnecessary info output.

fil_open_single_table_tablespace(): We call fsp_flags_try_adjust
only when when no errors has happened and server was not started
on read only mode and tablespace validation was requested or
flags contain other table options except low order bits to
FSP_FLAGS_POS_PAGE_SSIZE position.

fil_space_t::page_0_crypt_read removed.

Added test case innodb-first-page-read to test startup when
encryption is on and when encryption is off to check that not
for all tables page 0 is read on startup.

The doublewrite buffer pages must fit in the first InnoDB system
tablespace data file. The checks that were added in the initial patch
(commit 112b21da)
were at too high level and did not cover all cases.

innodb.log_data_file_size: Test all innodb_page_size combinations.

fsp_header_init(): Never return an error. Move the change buffer creation
to the only caller that needs to do it.

btr_create(): Clean up the logic. Remove the error log messages.

buf_dblwr_create(): Try to return an error on non-fatal failure.
Check that the first data file is big enough for creating the
doublewrite buffers.

buf_dblwr_process(): Check if the doublewrite buffer is available.
Display the message only if it is available.

recv_recovery_from_checkpoint_start_func(): Remove a redundant message
about FIL_PAGE_FILE_FLUSH_LSN mismatch when crash recovery has already
been initiated.

fil_report_invalid_page_access(): Simplify the message.

fseg_create_general(): Do not emit messages to the error log.

innobase_init(): Revert the changes.

trx_rseg_create(): Refactor (no functional change).

Removed this output.