… very little data. It seems that InnoDB performs better when a larger number of rows must be joined together (Q4.1, Q4…_table innodb_stats_on_metadata=off innodb_file_format=barracuda innodb_log_buffer_size=32M innodb_buffer_pool_instances=16 metadata_locks_hash_instances=32 table_open_cache_instances=8 sort_buffer_size=128k…
Post: Choosing a MySQL HA Solution - Post-Webinar Q&A
June 7, 2013 By Leave a Comment
…volume. So, in effect, you’re adding performance hit to performance hit. The other reason is because …top of a clustered filesystem with an external lock manager. You might say that MySQL/NDB Cluster…server up with –skip-grant-tables and insert a few rows into an InnoDB table, but trying to run…
Post: Is Synchronous Replication right for your app?
May 14, 2013 By 18 Comments
…bound on performance, only a upper bound. The best performance you can expect is modifying a given row …in a single table with a row for each stat; there are just a few hundred rows. When …row locks while it commits (which will take the 1 RTT). The other transactions will lock wait until the lock(…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… number of lock structs in row lock hash table is number of row lock structures allocated by all transactions. Note not same as number of locked rows – there are normally many rows… be 16K – page size, for full table scan or index scan read-ahead may be performed which can increase average read size…
Post: Innodb Table Locks
July 31, 2012 By 4 Comments
… table so we observe 2 table instances (note – same table gets counted twice) in use but zero tables are locked. Innodb does not need any row locks… so it performs locking reads to validate our theory: —TRANSACTION 12305, ACTIVE 9 sec mysql tables in use 2, locked 2 8316 lock struct(s…
Post: SELECT LOCK IN SHARE MODE and FOR UPDATE
August 6, 2006 By 51 Comments
…perform changes required. What is missing in Innodb locking.? In my oppinion few rather important peices missing in Locking implementation of Innodb are: Lock table Innodb can lock tables but it will still need to set row level locks which …
Post: InnoDB's gap locks
March 27, 2012 By 15 Comments
…, 3 row lock(s), undo log entries 1 MySQL thread id 3, OS thread handle 0x7f84a78ba700, query id 163 localhost msandbox TABLE LOCK table `test`.`t` trx id 72C lock mode IX RECORD LOCKS space id 19 page no 4 n bits 80 index `age` of table… 72C lock_mode X locks gap before rec If you have lot of gaps locks in your transactions affecting the concurrency and the performance…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…table_definition_cacheblogpercona.commanual table_lock_wait_timeoutblogpercona.commanual Table_locks_immediateblogpercona.commanual Table_locks_waitedblogpercona.commanual table_open_cacheblogpercona.commanual table…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
… to the table metadata, a table ALTER that alters a big table can keep executing without any hindrance, copying rows from the table with the… waiting for meta data locks. Why? Because in such a case no table open operation has to be performed. Let’s see this… | 3 | Waiting for table metadata lock | RENAME TABLE test_2 to test | | 10 | msandbox | localhost | test | Sleep | 37 | | NULL | +—-+———-+———–+——+———+——+———————————+—————————–+ 4 rows in set (0…
Post: Innodb locking and Foreign Keys
December 12, 2006 By 2 Comments
… row in PARENT table will be locked to perform update. The checks are performed “originating” from the table which you modify – if you update row in CHILD table… row will be locked. Same applies to PARENT table – if you will try to delete row in PARENT table lockup in CHILD table will be performed with row lock performed…
