Remote backend has bad performance due to termlist access

[richard]

When searching multiple databases with the remote backend, the matcher attempts to normalise the percentage weights based on the terms matching the top document. This is currently implemented by accessing the termlist, which is particular inefficient for remote documents, and results in very slow searches. The proper fix for this is related to ticket #216, but the fix for that is likely not to be suitable for backport to the 1.0 branch. However, it may be possible to make a simple fix for remote backends which is backportable, by calculating the percentage weight at the server end, rather than relying on the client end to normalise it.

[richard]

Patch special-casing the percentage calculation for remote databases

[richard]

Attached a patch which special cases the calculation of the percentage factor for remote databases, by using the value supplied by the remote end. This ought to help speed things up, without changing behaviour in any other way, but is untested (well, it passes the testsuite, but I've not checked it's performance characteristics yet, and I'm also pretty certain that the testsuite doesn't have adequate coverage of the percentage calculation stuff).

[richard]

Applied in revision [10822] to head. Still needs backporting to 1.0.

[olly]

Backported for 1.0.7.