…Innodb tables perform non locking reads, meaning unless you use some modifiers such as LOCK IN SHARE MODE or FOR UPDATE, SELECT statements will not lock…locking read (shared locks) for table2 table. It also applies to similar tables with where clause and joins. It is important for tables…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
…Query | 229 | Waiting for table metadata lock | ALTER TABLE test_2 DROP COLUMN c | | 7 | msandbox | localhost | test | Query | 195 | Waiting for table metadata lock…InnoDB; However, I feel that the CREATE TABLE should fail in such a case when the table already exists and there is no…
Post: SELECT LOCK IN SHARE MODE and FOR UPDATE
August 6, 2006 By 51 Comments
…locking mode which means they never lock any rows and just use old row versions if they were updated. All said above applies…FOR UPDATE to your select and reduce deadlocks if you’re updating selected rows. As query…; – A lot of shared locks on Innodb table but no updates. Supporting MySQL hints “…
Post: Choosing innodb_buffer_pool_size
November 3, 2007 By 39 Comments
…Innodb Buffer Size you can use. Typically you would see restriction applying…tables and otherwise running complex queries. It is usually much better to simply check it. Start MySQL With 10GB Innodb buffer pool for…for your Innodb tables but there are other things you need OS cache for – MyISAM tables…
Post: How fast is FLUSH TABLES WITH READ LOCK?
April 24, 2010 By 30 Comments
…Query | 62 | Flushing tables | flush tables with read lock | | 6 | root | localhost | test | Field List | 35 | Waiting for table | | | 7 | root | localhost | test | Query…lock. There is no reason to take a lock at all for backing up only InnoDB data. Completely lock…
Post: Innodb locking and Foreign Keys
December 12, 2006 By 2 Comments
…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. Innodb…for performance) to messages table you will have significant number of user ids locked in the user table which can stall queries working with users table…
Post: Innodb undo segment size and transaction isolation
January 12, 2011 By 3 Comments
…for other reasons such as taking row level locks which will prevent other transactions for execution, this however only applies…for that transaction to require state of any row in Innodb table at that point in time. If you use READ-COMMITTED mode Innodb…
Post: Falcon Storage Engine Design Review
January 12, 2007 By 19 Comments
…for some applications bad for others. There is large amount of applications out where which are optimized for Innodb…locking concurrency which can give you problems if you have lock intensive workload so many update queries have to wait for row level locks…
Post: Innodb performance gotcha w Larger queries.
August 28, 2009 By 7 Comments
…Innodb level, so I tried running the test with MyISAM tables instead. The process completed in 12 seconds for… .plt 18071 3.1113 no-vmlinux no-vmlinux (no symbols) Which shows some …for each time. if (trx->isolation_level select_lock_type != LOCK_NONE && trx->mysql_query_str) { /* Scan the MySQL query…
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
…for all the queries to finish, then projects the synchronously maintained incrementally refreshable materialized view that represents the output. There is no external locking…
