…descriptors_memory status variables in the …leak if query cache was used together with…mysql_set_permission was failing on Debian due to missing libdbd-mysql…MySQL 5.6 version, which removed MyISAM internal temporary table mutex contention. Bug fixed #1179978. Release notes for Percona Server for MySQL…
Post: Is Synchronous Replication right for your app?
May 14, 2013 By 18 Comments
… or capacitor-backed write cache), etc., but the principle is…MySQL replication from this instance, since MySQL replication is asynchronous. What about semi-sync MySQL… this table with a statement like this: UPDATE achievements SET count = count …times specified by this variable (default is 1 retry). …
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
…table that is already in the Table Cache, any query to a table that has a DDL operation waiting, will block. Why? Because MySQL…
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 5 Comments
…60 done Check for Table Cache Related Allocations There are cases when MySQL will allocate a lot of memory for table cache, especially if … reason. Connection Related Allocations Another set of buffers correspond to connections – orphaned prepared statements, user variables, huge network buffer (can …
Post: How much overhead is caused by on disk temporary tables
August 16, 2007 By 26 Comments
… we set key buffer to 128M ? mysql> show global status like “key%”; +————————+———+ | Variable_name | Value … for OS cache to keep temporary table. Results: mysql> select count(*) …mysql> set max_heap_table_size=1000000000; Query OK, 0 rows affected (0.00 sec) mysql> set tmp_table…
Post: table_cache negative scalability
November 16, 2009 By 23 Comments
…table_cache variable. So I decided to investigate what is really happening here. The “common sense” approach to tuning caches…MySQL 5.1 – in this version table_cache was significantly redone and split in table_open_cache and table_definition_cache… its own cache of file descriptors (set by innodb…
Post: Write contentions on the query cache
September 5, 2012 By 5 Comments
…| query end | 0.000004 | | closing tables | 0.000032 | | freeing …MySQL need so many accesses to the query cache lock? The answer is in the way the query cache…cache to be locked! More specifically, the size of the blocks is set by the value of the query_cache_min_res_unit variable…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 64 Comments
… stable. We can also get query_cache_ttl as session variable, which is very helpful for…from fast compression, such as QuickLZ. Results sets for most queries is highly compressible and… Query Cache content and operation can be presented as some INFORMATION_SCHEMA tables. Self Refresh MySQL Query Cache…
Post: MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark
March 11, 2013 By 7 Comments
…cache Star Schema Benchmark – Scale Factor 1 – Mysql…set (0.00 sec) mysql> select * from information_schema.global_status where variable_name like ‘%innodb%read%’; +—————————————+—————-+ | VARIABLE_NAME | VARIABLE… ); DROP TABLE IF EXISTS lineorder; CREATE TABLE IF…
Post: MySQL 5.5 and MySQL 5.6 default variable values differences
February 21, 2013 By 8 Comments
…the different tables and ran the query: mysql [localhost] {msandbox} (test) > select var55.variable_name,left(var55.variable_value,40) value55, left(var56.variable_value…here. table_open_cache is increased from 400 to 2000 by default. Good change making the default practical on larger set of …
