(mysql.info) archive-storage-engine

(mysql.info) federated-storage-engine
 
 14.8 The `ARCHIVE' Storage Engine
 =================================
 
 The `ARCHIVE' storage engine is used for storing large amounts of data
 without indexes in a very small footprint.
 
 The `ARCHIVE' storage engine is included in MySQL binary distributions.
 To enable this storage engine if you build MySQL from source, invoke
 `configure' with the -with-archive-storage-engine option.
 
 To examine the source for the `ARCHIVE' engine, look in the `sql'
 directory of a MySQL source distribution.
 
 You can check whether the `ARCHIVE' storage engine is available with
 this statement:
 
      mysql> SHOW VARIABLES LIKE 'have_archive';
 
 When you create an `ARCHIVE' table, the server creates a table format
 file in the database directory. The file begins with the table name and
 has an `.frm' extension. The storage engine creates other files, all
 having names beginning with the table name. The data and metadata files
 have extensions of `.ARZ' and `.ARM', respectively. An `.ARN' file may
 appear during optimization operations.
 
 The `ARCHIVE' engine supports `INSERT' and `SELECT', but not `DELETE',
 `REPLACE', or `UPDATE'. It does support `ORDER BY' operations, `BLOB'
 columns, and basically all but spatial data types (see 
 mysql-spatial-datatypes). The `ARCHIVE' engine uses row-level locking.
 
 *Storage:* Rows are compressed as they are inserted. The `ARCHIVE'
 engine uses `zlib' lossless data compression (see
 `http://www.zlib.net/'). You can use `OPTIMIZE TABLE' to analyze the
 table and pack it into a smaller format (for a reason to use `OPTIMIZE
 TABLE', see later in this section). Beginning with MySQL 5.0.15, the
 engine also supports `CHECK TABLE'.  There are several types of
 insertions that are used:
 
    * An `INSERT' statement just pushes rows into a compression buffer,
      and that buffer flushes as necessary. The insertion into the
      buffer is protected by a lock. A `SELECT' forces a flush to occur,
      unless the only insertions that have come in were `INSERT DELAYED'
      (those flush as necessary). See  insert-delayed.
 
    * A bulk insert is visible only after it completes, unless other
      inserts occur at the same time, in which case it can be seen
      partially. A `SELECT' never causes a flush of a bulk insert unless
      a normal insert occurs while it is loading.
 
 *Retrieval*: On retrieval, rows are uncompressed on demand; there is no
 row cache. A `SELECT' operation performs a complete table scan: When a
 `SELECT' occurs, it finds out how many rows are currently available and
 reads that number of rows.  `SELECT' is performed as a consistent read.
 Note that lots of `SELECT' statements during insertion can deteriorate
 the compression, unless only bulk or delayed inserts are used. To
 achieve better compression, you can use `OPTIMIZE TABLE' or `REPAIR
 TABLE'. The number of rows in `ARCHIVE' tables reported by `SHOW TABLE
 STATUS' is always accurate. See  optimize-table, 
 repair-table, and  show-table-status.
 
 *Additional resources*
 
    * A forum dedicated to the `ARCHIVE' storage engine is available at
      `http://forums.mysql.com/list.php?112'.
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