• Marko Mäkelä's avatar
    MDEV-25506 (3 of 3): Do not delete .ibd files before commit · 1bd681c8
    Marko Mäkelä authored
    This is a complete rewrite of DROP TABLE, also as part of other DDL,
    such as ALTER TABLE, CREATE TABLE...SELECT, TRUNCATE TABLE.
    
    The background DROP TABLE queue hack is removed.
    If a transaction needs to drop and create a table by the same name
    (like TRUNCATE TABLE does), it must first rename the table to an
    internal #sql-ib name. No committed version of the data dictionary
    will include any #sql-ib tables, because whenever a transaction
    renames a table to a #sql-ib name, it will also drop that table.
    Either the rename will be rolled back, or the drop will be committed.
    
    Data files will be unlinked after the transaction has been committed
    and a FILE_RENAME record has been durably written. The file will
    actually be deleted when the detached file handle returned by
    fil_delete_tablespace() will be closed, after the latches have been
    released. It is possible that a purge of the delete of the SYS_INDEXES
    record for the clustered index will execute fil_delete_tablespace()
    concurrently with the DDL transaction. In that case, the thread that
    arrives later will wait for the other thread to finish.
    
    HTON_TRUNCATE_REQUIRES_EXCLUSIVE_USE: A new handler flag.
    ha_innobase::truncate() now requires that all other references to
    the table be released in advance. This was implemented by Monty.
    
    ha_innobase::delete_table(): If CREATE TABLE..SELECT is detected,
    we will "hijack" the current transaction, drop the table in
    the current transaction and commit the current transaction.
    This essentially fixes MDEV-21602. There is a FIXME comment about
    making the check less failure-prone.
    
    ha_innobase::truncate(), ha_innobase::delete_table():
    Implement a fast path for temporary tables. We will no longer allow
    temporary tables to use the adaptive hash index.
    
    dict_table_t::mdl_name: The original table name for the purpose of
    acquiring MDL in purge, to prevent a race condition between a
    DDL transaction that is dropping a table, and purge processing
    undo log records of DML that had executed before the DDL operation.
    For #sql-backup- tables during ALTER TABLE...ALGORITHM=COPY, the
    dict_table_t::mdl_name will differ from dict_table_t::name.
    
    dict_table_t::parse_name(): Use mdl_name instead of name.
    
    dict_table_rename_in_cache(): Update mdl_name.
    
    For the internal FTS_ tables of FULLTEXT INDEX, purge would
    acquire MDL on the FTS_ table name, but not on the main table,
    and therefore it would be able to run concurrently with a
    DDL transaction that is dropping the table. Previously, the
    DROP TABLE queue hack prevented a race between purge and DDL.
    For now, we introduce purge_sys.stop_FTS() to prevent purge from
    opening any table, while a DDL transaction that may drop FTS_
    tables is in progress. The function fts_lock_table(), which will
    be invoked before the dictionary is locked, will wait for
    purge to release any table handles.
    
    trx_t::drop_table_statistics(): Drop statistics for the table.
    This replaces dict_stats_drop_index(). We will drop or rename
    persistent statistics atomically as part of DDL transactions.
    On lock conflict for dropping statistics, we will fail instantly
    with DB_LOCK_WAIT_TIMEOUT, because we will be holding the
    exclusive data dictionary latch.
    
    trx_t::commit_cleanup(): Separated from trx_t::commit_in_memory().
    Relax an assertion around fts_commit() and allow DB_LOCK_WAIT_TIMEOUT
    in addition to DB_DUPLICATE_KEY. The call to fts_commit() is
    entirely misplaced here and may obviously break the consistency
    of transactions that affect FULLTEXT INDEX. It needs to be fixed
    separately.
    
    dict_table_t::n_foreign_key_checks_running: Remove (MDEV-21175).
    The counter was a work-around for missing meta-data locking (MDL)
    on the SQL layer, and not really needed in MariaDB.
    
    ER_TABLE_IN_FK_CHECK: Replaced with ER_UNUSED_28.
    
    HA_ERR_TABLE_IN_FK_CHECK: Remove.
    
    row_ins_check_foreign_constraints(): Do not acquire
    dict_sys.latch either. The SQL-layer MDL will protect us.
    
    This was reviewed by Thirunarayanan Balathandayuthapani
    and tested by Matthias Leich.
    1bd681c8
trx0trx.cc 59.3 KB