[Xapian-discuss] xapian performance

[Olly Betts]

On Tue, Nov 21, 2006 at 07:20:30PM -0200, Fernando Nemec wrote:
> Sorry, Olly, but I'm not sure if I understand what this patch is
> intended to do.

The code used to encode and decode flint position lists in 0.9.9 and
earlier has a misfeature - it sometimes uses one bit more than is
intended (and required).  But the encoder and decoder both do this
so everything works (it's just a tiny amount larger than it could
be).

But unfortunately exactly when we get an extra bit depends on the
machine architecture.  Worse, it might also depend on compiler code
generation (I've not tried to demonstrate that, but it's conceivable).

Xapian databases are intended to be architecture independent, so we need
to fix this, even if it isn't dependent on the compiler.  This patch is
a quickly hacked up first attempt at a "flint database upgrader"
utility.

It's initially aimed at Arjen to allow him to test the "my_fls" patch.
Unless you have existing databases you can't rebuild in a reasonable
time, it's not really relevant.

Cheers,
    Olly