Re: Table marked as crashed and last (automatic?) repair failed

[Rick James]

I like the whole directory method. (I don't know if it is any "safer.)

CREATE TABLE ... ( ...
PRIMARY KEY (id) -- not a "secondary" key
UNIQUE (a) -- a secondary key
INDEX (b,c) -- another secondary key
) ENGINE=InnoDB

You effectively have 3 BTrees:
1. the entire dataset, ordered by id. Plus no dups on id.
2. an ordered list of (a,id). Plus no dups on a.
3. an ordered list of (b,c,id). There can be dups of b+c.

More subtly:
PRIMARY KEY(x,y)
INDEX(y,z) -- effectively a tree of (y,z,x) (no need to put x in twice)