Re: storage engine access to serialized version of a TABLE or TABLE_SHARE?

[Dmitry Lenev]

Hello Zardosht!

* Zardosht Kasheff <zardosht@stripped> [11/03/30 17:56]:
> Actually, let me put this question another way. Suppose during a call
> to handler::open, we return an error because the frm file generated
> from the TABLE* parameter does not match the frm file we stored on
> disk (due to some system crash at an inopportune time).
> 
> What, as a storage engine, can we do to get the user back to a well
> known state where the frm file he is using matches what we have on
> disk?

Here is what, AFAIK, NDB does.

If during call to handler::ha_open() it is discovered that local version
of table/.FRM is out-of-date HA_ERR_TABLE_DEF_CHANGED error is returned.

Upon getting such error code in server layer acquires appropriate locks,
invalidates corresponding entry in table definition cache and then
calls ha_create_table_from_engine() routine. The latter essentially calls
discover method of handlerton to get new version of .FRM and writes it
to disk.

Hope this helps!

-- 
Dmitry Lenev, Software Developer
Oracle Development SPB/MySQL, www.mysql.com

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