MySQL Archive: Difference between revisions

Revision as of 13:10, 6 December 2012

Revision as of 06:12, 8 March 2013

Line 23:

'''MySQL Archive''' is a storage engine for the [[MySQL]] [[relational database management system]]. Users can use this analytic storage engine to create a table that is “archive” only. Data cannot be deleted from this table, only added. The Archive engine uses a compression strategy based on the [[zlib]] library and it packs the rows using a bit header to represent nulls and removes all whitespace for character type fields. When completed, the row is inserted into the compression buffer and flushed to disk by an explicit flush table, a read, or the closing of the table.

One of the current restrictions of Archive tables is that they do not support any indexes, sothus you will be looking atnecessitating a table scan for any SELECT tasks. MySQL is examining index support for Archive tables in upcoming releases, but for nowhowever, one thing you can depend on to help table scan times is the fact that Archive tables are supported by the MySQL Query Cache, which can dramatically reduce response times for Archive table queries that are repetitively issued.<ref>http://web.archive.org/web/20100212100829/http://dev.mysql.com/tech-resources/articles/storage-engine.html The MySQL 5.0 Archive Storage Engine (archive date 20100212)</ref> MySQL is examining index support for Archive tables in upcoming releases.

The engine is not [[ACID]] compliant. Unlike [[OLTP]] engines, it uses a "stream" format to disk with no block boundaries. The head of the Archive file generated is a byte array representing the data format and contents of that file. In MySQL 5.1, a copy of the MySQL FRM file is stored in the header of each Archive file. The FRM file, which represents the definition of a table, allows an Archive file to be restored to a MySQL server if the Archive file is copied to the server.