Hi, Vassilis, On Jun 30, Vassilis Virvilis via discuss wrote:
Hi,
The question: Is uncompressing a myisam table when adding an index the expected behavior?
Yes. MyISAM does not support adding indexes inplace, so ALTER creates a new empty MyISAM table with indexes and copies the data over. The resulting table is uncompressed.
* If yes: why? Expanding the table behind the user's back is surprising...
Technically MyISAM could be able to add indexes inplace, it's just a feature that was never implemented. You can try this (disclaimer: I didn't test it). Create an empty table from your compressed one with CREATE TABLE LIKE. Add an index there. Compress it. Then copy your big MYD file over the the small MYD file and run myisamchk as you wanted. Better create a backup of your big table first, of course, or practice this on something small. Regards, Sergei Chief Architect, MariaDB Server and security@mariadb.org