7.1.2.3 Compressed 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 minimises 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.
• Can be uncompressed with myisamchk.

User Comments

Could it be possible to add double-quoted names
to allow using table names or column names that
are identical to reserved words or that include
some otherwise invalid characters ?

I think that a "double-quoted name" could be used
everywhere an identifier is allowed in the syntax
of MySQL, and this does not break Yacc parser
rules which can still stay deterministic for
faster performance...

Such an addition would also be consistant with
what Oracle or Access allow internally (so this
could allow easier porting of applications that
use these foreign databases, and could further
allow the implementation of open gateways, and
remote databases managed directly from a main
MySQL dictionnary, so that this would allow to
connect to any database using MySQL connectivity,
any any MySQL compliant tool...)

There's no description to the option
low_priority_updates. Someone should add it.

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