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.
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.
