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+New features compared to NISAM:
+
+- All file positions have type my_off_t; This enables one to use big
+ files (2^63 byte) by defining my_off_t to be longlong on OS that supports
+ big files.
+- When creating a table, one can now specify the maximum data file length.
+ This will be used to calculate the length of row pointers.
+- All key segments have their own language definition.
+- Some changes to support more types:
+ The biggest change is that the interface allows MY_ISAM will support
+ variable length integer types. (Only the interface is implemented)
+- All data is stored with low byte first; This makes the data machine
+ independent.
+- All number keys are stored with high byte first to give better packing.
+- Support for a true VARCHAR type; A VARCHAR column starts with a length
+ stored on 2 bytes.
+- Tables with VARCHAR may have fixed or dynamic record length.
+- There are now 2 different ways to pack keys:
+ - If the first key part is a space stripped CHAR, a VARCHAR or a BLOB the
+ 'packed' method is used. This only prefix-compresses the first
+ key part.
+ - In other cases prefix packing is used (This also includes the record
+ pointer into the prefix packing). A key may in the best case be
+ packed on 2 bytes.
+- VARCHAR and CHAR may be up to 65K
+- Index on BLOB and VARCHAR.
+- One can now have NULL in an index. This takes 0-1 bytes / key.
+- MYISAM will allow one to specify one AUTO_INCREMENT column; MYISAM will
+ automaticly update this on INSERT/UPDATE. The AUTO_INCREMENT value can be
+ reset with myisamchk.
+- Max key length will be 500 by default; In cases of longer keys than 250,
+ a bigger key block size than the default of 1024 byes is used for this key.
+- Max number of keys enlarged to 32 as default. This can be enlarged to 64
+ without having to recompile myisamchk.
+- There is a flag in the MYISAM header that tells if the index file (.MYI)
+ was closed correctly.
+- myisamchk will now mark tables as checked. 'myisamchk --fast' will only
+ check those tables that doesn't have this mark.
+- 'myisamchk -a' stores statistic for key parts (and not only for whole keys
+ as in NISAM).
+- Dynamic size rows will now be much less fragmented when mixing deletes with
+ update and insert. This is done by automaticly combine adjacent deleted
+ blocks and by extending blocks if the next block is deleted.
+- For dynamic size rows, the delete link contains a pointer to itself
+ (to make repairs easier).
+- myisampack (called pack_isam in NISAM) can pack BLOB and VARCHAR
+ columns.
+- One can now disable any key from update; In NISAM one could only disable
+ the last x keys.
+- One can have a UNIQUE constraint on anything (including BLOBS).
+ This is implemented by a key that contains a hashed number of the whole
+ record and before inserting a new record, MyISAM will check all records
+ with the same hash for dupplicates.
+- When creating the table, one can define that MyISAM should maintain
+ a CRC for the whole table (to make isamchk even better). In the case of
+ dynamic size rows, one will in this case get 1 byte checksum for each row.
+ (This is a great help for debugging, but it can also be used to keep
+ MyISAM table 'extra' safe.
+- Temporary tables will not write not flushed keys to file on close and
+ not wait on 'disk full' conditions.
+
+Interface changes compared to NISAM:
+
+- mi_create()
+ - keyinfo->seg must be allocated explicitely.
+ - One must put number of key segments in keyinfo