Push the patch of Jan Lindstrom: better comments
ha_innodb.cc:
Partial fix for Bug #12263 : we let InnoDB always to perform a rollback on the trx object if MySQL closes a connection; but we do print a warning to the .err log if an InnoDB transaction was active; we may remove that print later, since the situation really is not a bug; MySQL just is not aware that some cursor operation started an InnoDB transaction
data files. Previously, writes were flushed until the doublewrite
buffer was created. That would be too slow on systems where
os_file_flush() [or fsync(2)] is slow. (Bug #12125)
cursors for InnoDB. The idea of the patch is that if MySQL requests
a consistent read view, we open one when open a cursor, set is as the
active view to a transaction when fetch from the cursor, and close
together with cursor close. This patch is associated to bugs #11813,
#11832, and #11833. Contains after review fixes.
Since UNLOCK TABLES will commit the transaction (and thus release
all InnoDB locks held by it), it is unnecessary to release the
user-requested table locks separately.
If MySQL wrote to its binlog, but for some reason trx->update_undo and trx->insert_undo were NULL in InnoDB, then trx->commit_lsn was garbage, and InnoDB could assert in the log flush of trx_commit_complete_for_mysql() (Bug #9277)
Add a settable session variable innodb_support_xa; setting it to 0 can save up to 10 % of CPU time and 150 bytes of space in each undo log
trx0trx.h, trx0undo.c, trx0trx.c, trx0roll.c:
Enable XA if innodb_support_xa is not set to 0; make prepare to do log fsync's according to innodb_flush_log_at_trx_commit
Make InnoDB-5.0.3 to process log records of 4.1 undo log header create and reuse just like in 4.1; storing XID to the start of the undo log is a separately logged operation; this conforms to Rule 3 of InnoDB redo logging
Fix InnoDB critical bug #7496; we scan the InnoDB data dictionary also at a normal mysqld startup, and create the spaces, so that we know the mapping space id -> .ibd file name; fix an infinite loop if DISCARD TABLESPACE coincides with INSERT or some other table operation; fix a potential crash if DISCARD TABLESPACE coincides with a cascaded FOREIGN KEY operation in the same table; do not allow DISCARD TABLESPACE of a referenced table if FOREIGN_KEY_CHECKS=1
Print progress of background rollback of transactions with more than 1000 undo log entries
srv0start.c, trx0roll.c, log0recv.c, trx0roll.h:
Cleanup background rollback code in crash recovery; do not flush all modified pages from the buffer pool after a crash recovery: this makes mysqld accesible for users more quickly
