- Moving some of Database_qualidied_name methods into a new class
  Identifier_chain2.

- Changing the data type of the following variables from
  Database_qualified_name to Identifier_chain2:

  * q_pkg_proc in LEX::call_statement_start()
  * q_pkg_func in LEX::make_item_func_call_generic()

Rationale:

The data type of Database_qualified_name::m_db will be changed
to Lex_ident_db soon. So Database_qualified_name won't be able
to store the `pkg.routine` part of `db.pkg.routine` any more,
because `pkg` must not depend on lower-case-table-names.

- Changing the data type of the global variable any_db from
  LEX_CSTRING to Lex_ident_db

- Removing the dependency on system_charset_info from
  Lex_ident_fs::check_body(), using my_charset_utf8mb3_general_ci directly,
  because system_charset_info is initialized much later than any_db.
  system_charset_info cannot be changed dynamically any way.

- Removing the unsed old code from Lex_ident_fs::check_body().
  This code was last used in MySQL-4.0 and won't be used in the future.

- Replacing the old style inplace check_db_name() in make_table_name_list()
  to the new style non-modifying code
- Adding "const" qualifier to the "db" parameter to ha_discover_table_names()
  and its dependency functions.

- Adding a new class Lex_ident_db, to store normalized database names:
  lower-cased if lower-case-table-name says so,
  and checked to be a valid database name using Lex_ident_fs::check_db_name()

- Reusing the new class in parameters to functions:
    prepare_db_action()
    mysql_create_db()
    mysql_alter_db()
    mysql_rm_db()
    mysql_upgrade_db()

This change removed two old-style check_db_name() calls.

- Changing the global function ok_for_lower_case_names()
  into a method in class Lex_ident_fs.

- Changing a few functions/methods to get the database name
  as a "const LEX_CSTRING" instead of a "const char *".
  All these functions/methods use ok_for_lower_case_names()
  inside. This change helps to avoid new strlen() calls, and also
  removes a few old strlen() calls.

The function normalize_db_name() fully repeated the functionality
of the class DBNameBuffer. This patch  removes normalize_db_name()
and replaces it to a DBNameBuffer based code.

Changing LEX_CSTRING* parameters of LEX::make_sp_name() to Lex_ident_sys_st.

This makes the code clear because a value of Lex_ident_sys_st has
some guaranteed additional constraints over a base LEX_CSTRING:

- Its LEX_CSTRING::str is not NULL (sql_yacc.yy would abort otherwise)
- Its LEX_CSTRING::str is 0-terminated
- Its a valid utf8 string
- The string pointed by LEX_CSTRING::str was created on THD::mem_root

Also changing "pass by pointer" to "pass by reference",
as these parameters can never be NULL - they are Bison stack variables.

- Adding a class Lex_ident_fs, to store identifiers for on-disk
  database objects, such as databases, tables, triggers.

- Moving the validation code from check_db_name()
  to non-modifying methods in Lex_ident_fs:

    Lex_ident_fs::check_body()
    Lex_ident_fs::check_db_name()

  Adding a new method Lex_ident_fs::check_db_name_with_error(),
  which performs validation and raises an error on validation failure.

  Unlike the old function check_db_name(), the new class Lex_ident_fs
  does not lower-case the identifier during the validation.
  Lower-casing must be done before calling Lex_ident_fs validation methods.

- Adding a low level helper template class CharBuffer which can:
  * store exact or lower-cased strings with a short fixed maximum length
  * return the value as a LEX_CSTRING efficiently

- Adding a helper template class DBNameBuffer (deriving from CharBuffer), to
  allocate optionally lower-cased database identifiers on stack when relevant.
  Useful for temporary values which don't need to be allocated on MEM_ROOT.

- Using DBNameBuffer in mysql_change_db()

- Using DBNameBuffer in show_create_db()

- Renaming the parameter `check_for_path_char` to a more
  self-descriptive `disallow_path_chars`
- Renaming the variable `name_length` in check_table_name()
  to a more self-descriptive `char_length`.
- Fix the `while` loop in check_table_name() into a
  `for` loop and replace multiple {{char_length++}}
  (the former {{name_length++}}) statements to a signle increment
  statement in the `for` loop header.

MariaRocks is currently lagging behind the main branch of the RocksDB engine. This commit brings MariaRocks up to date with the latest release of RocksDB by backporting changes from Facebook’s MyRocks. These changes include API updates, bug fixes, and improvements for compatibility with RocksDB v8.1.1. Some system variables and metadata tables are modified to reflect the internal changes in RocksDB.

Additionally, this commit backports improved and more stable test cases from Facebook’s MyRocks, including tests for the write_unprepared isolation level of RocksDB. It also reverts workarounds for MDEV-29875 and MDEV-31057 and adds support for the latest compilation options.

The default value of the following system variables are changed:
* rocksdb_stats_level: 1 (kExceptHistogramOrTimers)
* rocksdb_wal_recovery_mode: 2 (kPointInTimeRecovery)

The following system variables are added:
* rocksdb_cancel_manual_compactions
* rocksdb_enable_iterate_bounds
* rocksdb_enable_pipelined_write
* rocksdb_enable_remove_orphaned_dropped_cfs
* rocksdb_manual_compaction_bottommost_level
* rocksdb_max_background_compactions
* rocksdb_max_background_flushes
* rocksdb_max_bottom_pri_background_compactions
* rocksdb_skip_locks_if_skip_unique_check
* rocksdb_track_and_verify_wals_in_manifest
* rocksdb_write_batch_flush_threshold

The following system variables are deprecated:
* rocksdb_hash_index_allow_collision
* rocksdb_new_table_reader_for_compaction_inputs

The following dynamic metadata table is added:
* INFORMATION_SCHEMA.ROCKSDB_LIVE_FILES_METADATA

The following status variables are added:
* rocksdb_manual_compactions_cancelled
* rocksdb_manual_compactions_pending

The following status variables are removed:
* rocksdb_block_cache_filter_bytes_evict
* rocksdb_block_cache_index_bytes_evict
* rocksdb_block_cachecompressed_hit
* rocksdb_block_cachecompressed_miss
* rocksdb_no_file_closes
* rocksdb_num_iterators
* rocksdb_number_deletes_filtered
* rocksdb_write_timedout

Add LOCK_ALTER_TABE_COPY bit to old_mode. Disables online copy by default,
but still allows to force it with explicit lock=none

... upon replicating online ALTER

When an online event is applied and slave_exec_mode is idempotent,
Write_rows_log_event::do_before_row_operations had reset
thd->lex->sql_command to SQLCOM_REPLACE.

This led to that a statement was detected as a row-type during binlogging,
and was logged as not standalone.

So the corresponding Gtid_log_event, when applied on replica, did not exit
early and created a new PSI transaction. Hence the difference with
non-online ALTER.

Pack these fields together:
event_owns_temp_buf
cache_type
slave_exec_mode
checksum_alg

Make them bitfields to fit a single 2-byte hole.

This saves 24 bytes per event.

SLAVE_EXEC_MODE_LAST_BIT is rewritten as

> SLAVE_EXEC_MODE_LAST= SLAVE_EXEC_MODE_IDEMPOTENT

to avoid a false-positive -Wbitfield-enum-conversion warning:
Bit-field 'slave_exec_mode' is not wide enough to store all enumerators of
'enum_slave_exec_mode'.

Replica honors its own binlog_row_image value when it sets up read_set.
When a slave thread is applying replicated row events in parallel with the
running online alter, we need all columns to be read from the table
(for the online alter logged row event) not only those that were present in
the pre-image for the replicated row event.

Avoid shrinking the set when online alter is running, i.e. leave it all set

s3 is read-only. No need to update to a read-only engine with LOCK=NONE.

Forbid Online for CONNECT.

Adding an auto_increment column online leads to an undefined behavior.
Basically any DEFAULTs that depend on a row order in the table, or on
the non-deterministic (in scope of the ALTER TABLE statement) function
is UB.

For example, NOW() is considered generally non-deterministic
(Item_func_now_utc is marked with VCOL_NON_DETERMINISTIC), but it's fixed
in scope of a single statement.

Same for any other function that depends only on the session/status vars
apart from its arguments.

Only two UB cases are known:
* adding new AUTO_INCREMENT column. Modifying the existing column may be
fine under certain circumstances, see MDEV-31058.
* adding new column with DEFAULT(nextval(...)). Modifying the existing
column is possible, since its value will be always present in the online
event, except for the NULL -> NOT NULL modification

Add a new virtual function that will increase the inserted rows count
for the insert log event and decrease it for the delete event.

Reuses Rows_log_event::m_row_count on the replication side, which was only
set on the logging side.

Forbid online for sequences. It doesn't work now and sequence tables are
always only one row, so not worth the extra complexity.

The deadlock was caused by too strong MDL acquired by the start ALTER.

Replica's ALTER TABLE replication consists of two phases:
1. Start ALTER (SA) -- the event is emittd in the very beginning,
allowing replication start ALTER in parallel
2. Commit ALTER (CA) -- ensures that master finishes successfully

CA is normally received by wait_for_master call.
If parallel DML was run, the following sequence will take place:

|- SA
|- DML
|- CA

If CA is handled after MDL upgrade, it'll will deadlock with DML.

While MDL is shared by the start ALTER wait for its 2nd part
to allow concurrent DMLs to grab the lock.

The fix uses wait_for_master reentrancy -- no need to avoid a second call
in the end of mysql_alter_table.

Since SA and CA are marked with FL_DDL, the DML issued in-between cannot be
rescheduled before or after them. However, SA "commits" (by he call of
write_bin_log_start_alter and, subsequently,
thd->wakeup_subsequent_commits) before the copy stage begins, unlocking
the DMLs to run on this table. That is, these DMLs will be executed
concurrently with the copy stage, making Online alter effective on replicas
as well

Co-authored-by: Nikita Malyavin (nikitamalyavin@gmail.com)

Make binlog_prepare_row_images accept image type as an argument.

1. Make online disk writes unlimited, same as filesort does.
2. Make proper error handling -- in 32-bit build IO_CACHE capacity limit is
4GB, so it is quite possible to overfill there.
3. Event_log::write_cache complicated with event reparsing, and as it was
proven by QA, contains some mistakes. Rewrite introbuce a simpler and much
faster version, not featuring reparsing and therefore copying a whole
buffer at once. This also disables checksums and crypto.
4. Handle read_log_event errors correctly: error returned is -1 (eof
signal for alter table), and my_error is not called. Call my_error and
always return 1. There's no test for this, since it shouldn't happen,
see the next bullet.
5. An event could be written partially in case of error, if it's bigger
than the IO_CACHE buffer. Restore the position where it was before the
error was emitted.

As a result, online alter is untied of several binlog variables, which was
a second aim of this patch.

Report correct algorithm in the error message.

Don't skip row_end if it wasn't set explicitly.

Also another segfault was caused by accessing rpl_write_set on slave during
the row update/delete.
The reason was a default_column_bitmaps() call, which also sets
rpl_write_set to NULL.
Previously, the related behavior was changed in commit afd3ee97ad, where
one such call was removed from Update_rows_log_event::do_exec_row, but the
same one was mistakenly left in Delete_rows_log_event. Now it's also
removed.

The correct (best) algorithm is now chosen for ALGORITHM=DEFAULT
and alter_algorithm=DEFAULT

See also MDEV-30906

Group all the checks in online_alter_check_supported().

There is now two groups of checks:
1. A technical availability of online, that is checked before open_tables,
and affects table_list->lock_type. It's supposed to be safe to make it
TL_READ even if COPY algorithm will fall back to not-online, since MDL is
SHARED_UPGRADEABLE anyway.
2. An 'online' availability for a COPY algorithm. It can be done as late as
just before the copy_data_between_tables call. The lock_type influence is
disclosed above, so the only other place it affects is
Alter_info::supports_lock, where `online` flag is only used to decide
whether to report the error at the inplace preparation stage. We'd want to
make that at the last resort, which is COPY preparation, if no algorithm is
chosen by the user. So it's event better now.

Some changes are required to the autoinc support detection, as the check
now happens after mysql_prepare_alter_table:
* alter_info->drop_list is empty
* instead, dropped columns are in tmp_set
* alter_info->create_list now has every field that's in the new table.
* the column definition's change.str will be nonnull whether the column
  remains in the new table (vs whether it was changed, as before).
  But it also has `field` field set.
* IF EXISTS doesn't have to be dealt anymore

This infers that the changes are now checked in more detail: a field's
definition shouldn't be changed, vs a field shouldn't be mentioned in
the CHANGE list, as it was before. This is reflected by the line 193 test.

Also update abi declarations. The abi itself is unchanged, since const
doesn't affect C-style exported name.

disabie view-protocol for certain places:
1. While a transaction is in progress: a view gets locked for a
transaction duration, so DROP VIEW from a servicing conneciton
deadlocks. We can't just disable servicing connection, as
CREATE VIEW and DROP VIEW commit implicitly.
2. For querying Opened_table_definitions: the actual query executed
is `SELECT * FROM mysqltest_tmp_v`, then the view is dropped

Skip more rpl-related error handling.
Also move the error check inside if (table) -- otherwise the error
should be handled already.

Online alter and replication paths differ quite noticeably. It's time to
fix the mess. Online alter has to unpack the old table's data
(here conv_table), and then convert, while replication requires more
sophisticated track: handle possible conversions, treat extra replica
fields, and carefully deduce master's record length.

* Extract unpack_field.
* handle the unpacking progress through a state machine presented by
  Unpack_record_state struct.
* Stick most of the online alter unpacking together under a single
  conditional branch.

When column is changed to autoinc, ALTER TABLE may update zero/NULL values,
if NO_AUTO_VALUE_ON_ZERO mode is not enabled.

Forbid this for LOCK=NONE for the unreliable cases.
The cases are described in online_alter_check_autoinc.