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Showing entries 1 to 6

Displaying posts with tag: data dictionary (reset)

InnoDB scalability issues due to tables without primary keys
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Each day there is probably work done to improve performance of the InnoDB storage engine and remove bottlenecks and scalability issues. Hence there was another one I wanted to highlight: Scalability issues due to tables without primary keys. This scalability issue is caused by the usage of tables without primary keys. This issue typically shows itself as contention on the InnoDB dict_sys mutex. Now the dict_sys mutex controls access to the data dictionary. This mutex is used at various important places throughout the InnoDB code and …

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InnoDB scalability issues due to tables without primary keys
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Each day there is probably work done to improve performance of the InnoDB storage engine and remove bottlenecks and scalability issues. Hence there was another one I wanted to highlight:

Scalability issues due to tables without primary keys

This scalability issue is caused by the usage of tables without primary keys. This issue typically shows itself as contention on the InnoDB dict_sys mutex. Now the dict_sys mutex controls access to the data dictionary. This mutex is used at various places. I will only mention a few of them:

  • During operations such as opening and closing table handles, or
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MySQL 5.6: Data dictionary LRU
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In MySQL 5.6 we’ve added a new feature that closes and unloads table instances from the InnoDB internal data dictionary, once a user configurable threshold is reached. This ends the situation where you could have hundreds of megabytes caching rarely used entries until the server was restarted and will be particularly appreciated by hosting and software as a service providers.

For this we’ve used an existing MySQL config variable table-definition-cache.  This cache limit is a soft limit. This means that if …

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Drizzle’s Data Dictionary and Global Status
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With the recent news by Brian about the Data Dictionary in Drizzle replacing the INFORMATION_SCHEMA, I was looking into the server status variables (aka INFORMATION_SCHEMA.GLOBAL_STATUS) and I came across an interesting discovery.

select * from data_dictionary.global_status;
...
| Table_locks_immediate      | 0              |
| Table_locks_waited         | 0              |
| Threads_connected          | 8134064        |
| Uptime                     | 332            |
| Uptime_since_flush_status  | 332            |
+----------------------------+----------------+
51 rows in set …
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Fixing InnoDB IMPORT TABLESPACE Error: ERROR 1030 (HY000): Got error -1 from storage engine
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SetupWe have one InnoDB file per table on our database, which was set with the following option: innodb_file_per_table.This allows me to portably transport Innodb files on a system level with minimal hassle, and is much faster than mysqldump, as these tables are several GB each.ProblemWhen transporting an .idb file from one server to another, I ran into the following error:ERROR 1030 (HY000): Got

Blank VIEW_DEFINITION?
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As I putter around the MySQL INFORMATION_SCHEMA, I am finding lots of undocumented behavior for fields that should be straightforward. For example, the VIEWS table holds information about views, and the VIEW_DEFINITION field contains the view definition, right?

Well, when I was looking at the VIEW_DEFINITION today, I noticed an odd thing. Even though I had permissions to see the view definition (as proven by the SHOW CREATE VIEW command), the INFORMATION_SCHEMA.VIEWS table sometimes came up blank for the VIEW_DEFINITION. I had to figure out why, and now that I know, I’m …

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Showing entries 1 to 6

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