[Xapian-discuss] How to rebuild database from scratch without preventing searches

[Richard Boulton]

On 12 April 2011 14:10, William Crawford <william at sciencephoto.co.uk> wrote:
> We'd like to rebuild the database while still allowing searches to proceed,
> naturally ... what's the, uh, "recommended" way to do this? Build into a
> temporary copy and move a symlink? Is there any way to clear the contents and
> start over without removing the existing version so readers can continue to
> work (other than scanning through all the existing documents and removing them
> ...)?

Don't use a symlink - if a database is being opened for reading while
the symlink is changed, some tables may be opened from the old db, and
some from the new, causing a (false) report of a corrupted database).

What you want to use is a stub database:
http://xapian.org/docs/overview.html (and search for stub database).

Basically, this is a text file which points to one or more other
databases.  You can open a Xapian::Database by pointing to a stub
database, and it will read it and open the databases it points to,
returning them as the Xapian::Database.  Also, because it's a single
file, you can use rename to atomically replace it with a new file, to
swap to a file pointing to a new set of databases.

If you work this out, we really need to write this up in the admin
guide (http://xapian.org/docs/admin_notes.html) - if anyone's able to
provide a patch to add this, that'd be great.

-- 
Richard