[Xapian-discuss] get previous term, order of terms, 8-byte position info

[Richard Boulton]

On 21 August 2012 12:50, Előd Biszak <biszakelod at gmail.com> wrote:
> I'm a hungarian developer, i'm new using Xapian, but i find it fascinating.
> Altough I have some questions about it.
>
>     Is there a way to go through the terms of the database backwards? So
> given a term is there a way to get the previous one?

No, this isn't possible with the current code.  It's been something
we'd like to have for a long while, but it's never been implemented.
There's a long running ticket about it:
http://trac.xapian.org/ticket/52

>     I want to hold extra information in the position information of a term.
> Is there a way to use 8-byte position information?

No, but look into "document values", which can hold arbitrary
information for each document in a way which can be accessed
efficiently during the search.
http://getting-started-with-xapian.readthedocs.org/en/latest/concepts/indexing/values.html

>     Is there a way to manipulate the order of terms?

No, terms always occur in posting lists in ascending order of docid.
The matcher relies on this fact so that it can iterate through all the
posting lists involved in a query simultaneously, and match the
entries for corresponding documents together.

-- 
Ricahrd