Innodb_stats_on_metadata

INFORMATION_SCHEMA is usually the place to go when you want to get facts about a system (how many tables do we have? what are the largest tables? What is data size and index size for table t?, etc). SHOW ENGINE INNODB STATUS output to it every seconds, approximately. SET GLOBAL innodb_ stats_on _metadata = with constraint query (i.e. in PHPMyAdmin) like this. As InnoDB executes each UPDATE, it first acquires an exclusive lock for each row, and then determines whether to modify it.

If InnoDB does not modify the row and innodb _locks_unsafe_for_binlog is enable it releases the lock. TABLES or INFORMATION_SCHEMA. Description: Size in bytes of the InnoDB memory pool used for storing information about internal data structures. Defaults to 8MB, if your application has many tables and a large structure, and this is exceede operating system memory will be allocated and warning messages written to the error log, in which case you should increase this value. In this particular case, I think the INFORMATION_SCHEMA is a red herring.

InnoDB is fairly light weight when it gathers table and index statistics. In the default compiled in InnoDB for most users it will do random dives in to the index and samples the page to try to ascertain the cardinality (selectivity) of the index for use by the optimizer. This being the case, not only is this done. Enabling innodb_stats_on_metadata may reduce access speed for schemas that have a large number of tables or indexes, and reduce stability of execution plans for queries that involve InnoDB tables. Leaving it off will provide more stable Query Execution plans, but the index statistics grow stale quickly in a heavy-write environment.

Ask Question Asked years,. You could try to stabilize things a little by enabling innodb_stats_on_metadata. The recalculation can be triggered with either analyze table or by modifying more than of the rows in the table.

The number of rows modified is not persisted. Peter, Implementation is different, but declared functionality works incorrectly. Please look into my patch with test-cases.

MyISAM and InnoDB has identical behavior for nulls_equal and nulls_unequal, and different behavior for nulls_ignored. When it is turned off, Innnodb statistics are not updated during those operations. For schemas that have a large number of tables or indexes, this can have a positive effect on access speeds. It can also improve the stability of execution plans that involve Innodb tables. Changing the setting requires privileges sufficient to set global system variables (see Section . “System Variable Privileges” ) and immediately affects the operation of all connections.

Disabling triggers speed up batch processings. For simple UPDATE cases where it is necessary, POSTGRES allows deferrable foreign keys. Summary: Make innodb_stats_on_metadata a session variable and enforced for both transient and persistent stats. Test Plan: added a new test: innodb. PARTITIONS table, InnoDB index statistics as shown in the output of statements such as SHOW INDEX were update even with innodb_stats_on_metadata =OFF.

Starting with version 5. Beginning with MySQL version 5. By default, this option is disabled. When innodb_file_per_table is enabled (the default in .and higher), InnoDB stores the data and indexes for each newly created table in a separate. DML期间也不作动态统计了。因此这个参数配置成off更合理些（默认是on）. The value of innodb _ stats _method is not honored when innodb _ stats _persistent=ON.

We have used Ubuntu xenial 16.