If a crash occurs during ALTER TABLE…ALGORITHM=COPY, InnoDB would spend
a lot of time rolling back writes to the intermediate copy of the table.
To reduce the amount of busy work done, a work-around was introduced in
commit fd069e2bb3 in MySQL 4.1.8 and 5.0.2,
to commit the transaction after every 10,000 inserted rows.
A proper fix would have been to disable the undo logging altogether and
to simply drop the intermediate copy of the table on subsequent server
startup. This is what happens in MariaDB 10.3 with MDEV-14717,MDEV-14585.
In MariaDB 10.2, the intermediate copy of the table would be left behind
with a name starting with the string #sql.
This is a backport of a bug fix from MySQL 8.0.0 to MariaDB,
contributed by jixianliang <271365745@qq.com>.
Unlike recent MySQL, MariaDB supports ALTER IGNORE. For that operation
InnoDB must for now keep the undo logging enabled, so that the latest
row can be rolled back in case of an error.
In Galera cluster, the LOAD DATA statement will retain the existing
behaviour and commit the transaction after every 10,000 rows if
the parameter wsrep_load_data_splitting=ON is set. The logic to do
so (the wsrep_load_data_split() function and the call
handler::extra(HA_EXTRA_FAKE_START_STMT)) are joint work
by Ji Xianliang and Marko Mäkelä.
The original fix:
Author: Thirunarayanan Balathandayuthapani <thirunarayanan.balathandayuth@oracle.com>
Date: Wed Dec 2 16:09:15 2015 +0530
Bug#17479594 AVOID INTERMEDIATE COMMIT WHILE DOING ALTER TABLE ALGORITHM=COPY
Problem:
During ALTER TABLE, we commit and restart the transaction for every
10,000 rows, so that the rollback after recovery would not take so long.
Fix:
Suppress the undo logging during copy alter operation. If fts_index is
present then insert directly into fts auxiliary table rather
than doing at commit time.
ha_innobase::num_write_row: Remove the variable.
ha_innobase::write_row(): Remove the hack for committing every 10000 rows.
row_lock_table_for_mysql(): Remove the extra 2 parameters.
lock_get_src_table(), lock_is_table_exclusive(): Remove.
Reviewed-by: Marko Mäkelä <marko.makela@oracle.com>
Reviewed-by: Shaohua Wang <shaohua.wang@oracle.com>
Reviewed-by: Jon Olav Hauglid <jon.hauglid@oracle.com>
Traditionally, DROP TABLE and TRUNCATE TABLE discarded any locks that
may have been held on the table. This feels like an ACID violation.
Probably most occurrences of it were prevented by meta-data locks (MDL)
which were introduced in MySQL 5.5.
dict_table_t::n_foreign_key_checks_running: Reduce the number of
non-debug checks.
lock_remove_all_on_table(), lock_remove_all_on_table_for_trx(): Remove.
ha_innobase::truncate(): Acquire an exclusive InnoDB table lock
before proceeding. DROP TABLE and DISCARD/IMPORT were already doing
this.
row_truncate_table_for_mysql(): Convert the already started transaction
into a dictionary operation, and do not invoke lock_remove_all_on_table().
row_mysql_table_id_reassign(): Do not call lock_remove_all_on_table().
This function is only used in ALTER TABLE...DISCARD/IMPORT TABLESPACE,
which is already holding an exclusive InnoDB table lock.
TODO: Make n_foreign_key_checks running a debug-only variable.
This would require two fixes:
(1) DROP TABLE: Exclusively lock the table beforehand, to prevent
the possibility of concurrently running foreign key checks (which
would acquire a table IS lock and then record S locks).
(2) RENAME TABLE: Find out if n_foreign_key_checks_running>0 actually
constitutes a potential problem.
MDEV-14511 tried to avoid some consistency problems related to InnoDB
persistent statistics. The persistent statistics are being written by
an InnoDB internal SQL interpreter that requires the InnoDB data dictionary
cache to be locked.
Before MDEV-14511, the statistics were written during DDL in separate
transactions, which could unnecessarily reduce performance (each commit
would require a redo log flush) and break atomicity, because the statistics
would be updated separately from the dictionary transaction.
However, because it is unacceptable to hold the InnoDB data dictionary
cache locked while suspending the execution for waiting for a
transactional lock (in the mysql.innodb_index_stats or
mysql.innodb_table_stats tables) to be released, any lock conflict
was immediately be reported as "lock wait timeout".
To fix MDEV-14941, an attempt to reduce these lock conflicts by acquiring
transactional locks on the user tables in both the statistics and DDL
operations was made, but it would still not entirely prevent lock conflicts
on the mysql.innodb_index_stats and mysql.innodb_table_stats tables.
Fixing the remaining problems would require a change that is too intrusive
for a GA release series, such as MariaDB 10.2.
Thefefore, we revert the change MDEV-14511. To silence the
MDEV-13201 assertion, we use the pre-existing flag trx_t::internal.
If InnoDB is killed while ALTER TABLE...ALGORITHM=COPY is in progress,
after recovery there could be undo log records some records that were
inserted into an intermediate copy of the table. Due to these undo log
records, InnoDB would resurrect locks at recovery, and the intermediate
table would be locked while we are trying to drop it. This would cause
a call to row_rename_table_for_mysql(), either from
row_mysql_drop_garbage_tables() or from the rollback of a RENAME
operation that was part of the ALTER TABLE.
row_rename_table_for_mysql(): Do not attempt to parse FOREIGN KEY
constraints when renaming from #sql-something to #sql-something-else,
because it does not make any sense.
row_drop_table_for_mysql(): When deferring DROP TABLE due to locks,
do not rename the table if its name already starts with the #sql-
prefix, which is what row_mysql_drop_garbage_tables() uses.
Previously, the too strict prefix #sql-ib was used, and some
tables were renamed unnecessarily.
In CREATE SEQUENCE or CREATE TEMPORARY SEQUENCE, we should not start
an InnoDB transaction for inserting the sequence status record into
the underlying no-rollback table. Because we did this, a debug assertion
failure would fail in START TRANSACTION WITH CONSISTENT SNAPSHOT after
CREATE TEMPORARY SEQUENCE was executed.
row_ins_step(): Do not start the transaction. Let the caller do that.
que_thr_step(): Start the transaction before calling row_ins_step().
row_ins_clust_index_entry(): Skip locking and undo logging for no-rollback
tables, even for temporary no-rollback tables.
row_ins_index_entry(): Allow trx->id==0 for no-rollback tables.
row_insert_for_mysql(): Do not start a transaction for no-rollback tables.
Now that MDEV-14717 made RENAME TABLE crash-safe within InnoDB,
it should be safe to drop the #sql- tables within InnoDB during
crash recovery. These tables can be one of two things:
(1) #sql-ib related to deferred DROP TABLE (follow-up to MDEV-13407)
or to table-rebuilding ALTER TABLE...ALGORITHM=INPLACE
(since MDEV-14378, only related to the intermediate copy of a table),
(2) #sql- related to the intermediate copy of a table during
ALTER TABLE...ALGORITHM=COPY
We will not drop tables whose name starts with #sql2, because
the server can be killed during an ALGORITHM=COPY operation at
a point where the original table was renamed to #sql2 but the
finished intermediate copy was not yet renamed from #sql-
to the original table name.
InnoDB in MariaDB 10.2 appears to only write MLOG_FILE_RENAME2
redo log records during table-rebuilding ALGORITHM=INPLACE operations.
We must write the records for any .ibd file renames, so that the
operations are crash-safe.
If InnoDB is killed during a RENAME TABLE operation, it can happen that
the transaction for updating the data dictionary will be rolled back.
But, nothing will roll back the renaming of the .ibd file
(the MLOG_FILE_RENAME2 only guarantees roll-forward), or for that matter,
the renaming of the dict_table_t::name in the dict_sys cache. We introduce
the undo log record TRX_UNDO_RENAME_TABLE to fix this.
fil_space_for_table_exists_in_mem(): Remove the parameters
adjust_space, table_id and some code that was trying to work around
these deficiencies.
fil_name_write_rename(): Write a MLOG_FILE_RENAME2 record.
dict_table_rename_in_cache(): Invoke fil_name_write_rename().
trx_undo_rec_copy(): Set the first 2 bytes to the length of the
copied undo log record.
trx_undo_page_report_rename(), trx_undo_report_rename():
Write a TRX_UNDO_RENAME_TABLE record with the old table name.
row_rename_table_for_mysql(): Invoke trx_undo_report_rename()
before modifying any data dictionary tables.
row_undo_ins_parse_undo_rec(): Roll back TRX_UNDO_RENAME_TABLE
by invoking dict_table_rename_in_cache(), which will take care
of both renaming the table and the file.
The InnoDB background DROP TABLE queue is something that we should
really remove, but are unable to until we remove dict_operation_lock
so that DDL and DML operations can be combined in a single transaction.
Because the queue is not persistent, it is not crash-safe. We should
in some way ensure that the deferred-dropped tables will be dropped
after server restart.
The existence of two separate transactions complicates the error handling
of CREATE TABLE...SELECT. We should really not break locks in DROP TABLE.
Our solution to these problems is to rename the table to a temporary
name, and to drop such-named tables on InnoDB startup. Also, the
queue will use table IDs instead of names from now on.
check-testcase.test: Ignore #sql-ib*.ibd files, because tables may enter
the background DROP TABLE queue shortly before the test finishes.
innodb.drop_table_background: Test CREATE...SELECT and the creation of
tables whose file name starts with #sql-ib.
innodb.alter_crash: Adjust the recovery, now that the #sql-ib tables
will be dropped on InnoDB startup.
row_mysql_drop_garbage_tables(): New function, to drop all #sql-ib tables
on InnoDB startup.
row_drop_table_for_mysql_in_background(): Remove an unnecessary and
misplaced call to log_buffer_flush_to_disk(). (The call should have been
after the transaction commit. We do not care about flushing the redo log
here, because the table would be dropped again at server startup.)
Remove the entry from the list after the table no longer exists.
If server shutdown has been initiated, empty the list without actually
dropping any tables. They will be dropped again on startup.
row_drop_table_for_mysql(): Do not call lock_remove_all_on_table().
Instead, if locks exist, defer the DROP TABLE until they do not exist.
If the table name does not start with #sql-ib, rename it to that prefix
before adding it to the background DROP TABLE queue.
The InnoDB background DROP TABLE queue is something that we should
really remove, but are unable to until we remove dict_operation_lock
so that DDL and DML operations can be combined in a single transaction.
Because the queue is not persistent, it is not crash-safe. In stable
versions of MariaDB, we can only try harder to drop all enqueued
tables before server shutdown.
row_mysql_drop_t::table_id: Replaces table_name.
row_drop_tables_for_mysql_in_background():
Do not remove the entry from the list as long as the table exists.
In this way, the table should eventually be dropped.
Allow DROP TABLE `#mysql50##sql-...._.` to drop tables that were
being rebuilt by ALGORITHM=INPLACE
NOTE: If the server is killed after the table-rebuilding ALGORITHM=INPLACE
commits inside InnoDB but before the .frm file has been replaced, then
the recovery will involve something else than DROP TABLE.
NOTE: If the server is killed in a true inplace ALTER TABLE commits
inside InnoDB but before the .frm file has been replaced, then we
are really out of luck. To properly handle that situation, we would
need a transactional mysql.ddl_fixup table that directs recovery to
rename or remove files.
prepare_inplace_alter_table_dict(): Use the altered_table->s->table_name
for generating the new_table_name.
table_name_t::part_suffix: The start of the partition name suffix.
table_name_t::dbend(): Return the end of the schema name.
table_name_t::dblen(): Return the length of the schema name, in bytes.
table_name_t::basename(): Return the name without the schema name.
table_name_t::part(): Return the partition name, or NULL if none.
row_drop_table_for_mysql(): Assert for #sql, not #sql-ib.
dict_stats_exec_sql(): Expect the caller to always provide a transaction.
Remove some redundant assertions. The caller must hold dict_sys->mutex,
but holding dict_operation_lock is only necessary for accessing
data dictionary tables, which we are not accessing.
dict_stats_save_index_stat(): Acquire dict_sys->mutex
for invoking dict_stats_exec_sql().
dict_stats_save(), dict_stats_update_for_index(), dict_stats_update(),
dict_stats_drop_index(), dict_stats_delete_from_table_stats(),
dict_stats_delete_from_index_stats(), dict_stats_drop_table(),
dict_stats_rename_in_table_stats(), dict_stats_rename_in_index_stats(),
dict_stats_rename_table(): Use a single caller-provided
transaction that is started and committed or rolled back by the caller.
dict_stats_process_entry_from_recalc_pool(): Let the caller provide
a transaction object.
ha_innobase::open(): Pass a transaction to dict_stats_init().
ha_innobase::create(), ha_innobase::discard_or_import_tablespace():
Pass a transaction to dict_stats_update().
ha_innobase::rename_table(): Pass a transaction to
dict_stats_rename_table(). We do not use the same transaction
as the one that updated the data dictionary tables, because
we already released the dict_operation_lock. (FIXME: there is
a race condition; a lock wait on SYS_* tables could occur
in another DDL transaction until the data dictionary transaction
is committed.)
ha_innobase::info_low(): Pass a transaction to dict_stats_update()
when calculating persistent statistics.
alter_stats_norebuild(), alter_stats_rebuild(): Update the
persistent statistics as well. In this way, a single transaction
will be used for updating the statistics of a whole table, even
for partitioned tables.
ha_innobase::commit_inplace_alter_table(): Drop statistics for
all partitions when adding or dropping virtual columns, so that
the statistics will be recalculated on the next handler::open().
This is a refactored version of Oracle Bug#22469660 fix.
RecLock::add_to_waitq(), lock_table_enqueue_waiting():
Do not allow a lock wait to occur for updating statistics
in a data dictionary transaction, such as DROP TABLE. Instead,
return the previously unused error code DB_QUE_THR_SUSPENDED.
row_merge_lock_table(), row_mysql_lock_table(): Remove dead code
for handling DB_QUE_THR_SUSPENDED.
row_drop_table_for_mysql(), row_truncate_table_for_mysql():
Drop the statistics as part of the data dictionary transaction.
After TRUNCATE TABLE, the statistics will be recalculated on
subsequent ha_innobase::open(), similar to how the logic after
the above-mentioned Oracle Bug#22469660 fix in
ha_innobase::commit_inplace_alter_table() works.
btr_defragment_thread(): Use a single transaction object for
updating defragmentation statistics.
dict_stats_save_defrag_stats(), dict_stats_save_defrag_stats(),
dict_stats_process_entry_from_defrag_pool(),
dict_defrag_process_entries_from_defrag_pool(),
dict_stats_save_defrag_summary(), dict_stats_save_defrag_stats():
Add a parameter for the transaction.
dict_stats_empty_table(): Make public. This will be called by
row_truncate_table_for_mysql() after dropping persistent statistics,
to clear the memory-based statistics as well.
THD::vers_update_trt, trx_t::vers_update_trt, trx_savept_t::vers_update_trt:
Remove. Instead, determine from trx_t::mod_tables whether versioned
columns were affected by the transaction.
handlerton::prepare_commit_versioned: Replaces vers_get_trt_data.
Return the transaction start ID and also the commit ID, in case
the transaction modified any system-versioned columns (0 if not).
TR_table::store_data(): Remove (merge with update() below).
TR_table::update(): Add the parameters start_id, end_id.
ha_commit_trans(): Remove a condition on SQLCOM_ALTER_TABLE.
If we need something special for ALTER TABLE...ALGORITHM=INPLACE,
that can be done inside InnoDB by modifying trx_t::mod_tables.
innodb_prepare_commit_versioned(): Renamed from innodb_get_trt_data().
Check trx_t::mod_tables to see if any changes to versioned columns
are present.
trx_mod_table_time_t: A pair of logical timestamps, replacing the
undo_no_t in trx_mod_tables_t. Keep track of not only the first
modification to a persistent table in each transaction, but also
the first modification of a versioned column in a table.
dtype_t, dict_col_t: Add the accessor is_any_versioned(), to check
if the type refers to a system-versioned user or system column.
upd_t::affects_versioned(): Check if an update affects a versioned
column.
trx_undo_report_row_operation(): If a versioned column is affected
by the update, invoke trx_mod_table_time_t::set_versioned().
trx_rollback_to_savepoint_low(): If all changes to versioned columns
were rolled back, invoke trx_mod_table_time_t::rollback_versioned(),
so that trx_mod_table_time_t::is_versioned() will no longer hold.
