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GNU Info (mysql.info)Compressed formatCompressed Table Characteristics ................................ This is a read-only type that is generated with the optional `myisampack' tool (`pack_isam' for `ISAM' tables): * All MySQL distributions, even those that existed before MySQL went GPL, can read tables that were compressed with `myisampack'. * Compressed tables take very little disk space. This minimizes disk usage, which is very nice when using slow disks (like CD-ROMs). * Each record is compressed separately (very little access overhead). The header for a record is fixed (1-3 bytes) depending on the biggest record in the table. Each column is compressed differently. Some of the compression types are: - There is usually a different Huffman table for each column. - Suffix space compression. - Prefix space compression. - Numbers with value `0' are stored using 1 bit. - If values in an integer column have a small range, the column is stored using the smallest possible type. For example, a `BIGINT' column (8 bytes) may be stored as a `TINYINT' column (1 byte) if all values are in the range `0' to `255'. - If a column has only a small set of possible values, the column type is converted to `ENUM'. - A column may use a combination of the above compressions. * Can handle fixed- or dynamic-length records, but not `BLOB' or `TEXT' columns. * Can be uncompressed with `myisamchk'. automatically generated by info2www version 1.2.2.9 |