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From Søren Hilmer ...@widetrail.dk>
Subject Re: The state of the fulltext search
Date Mon, 12 May 2008 21:10:03 GMT
Hi

As you know. I did some work on the ideas of indexing views, but as Jan 
explains, there was no good way of doing it. I do not believe that the 
experiments has significant value, if the goal now is to move to JSearch and 
do Document indexing instead of Views indexing.

I did post a few patches for couchdb4j, which has made it into trunk 
(couchdb4j trunk that is) and thus makes it easier to get the existing 
codebase up and running. Couchdb4j, still has some issues with handling Views 
correctly (it seams to be coded around an old couchdb model, where Views are 
tied to Documents).

From Jun's intro to JSearch, that seams to be a nice fit for couchdb. I am 
looking forward to trying it out.

Have fun
   Søren

On Saturday 10 May 2008 20:56, Jan Lehnardt wrote:
> Heya folks,
> this mail is an introduction for Jun and Bo from IBM who
> would like to contribute JSearch[1] to CouchDB. JSearch
> sits on top of Lucene so this clearly affects our fulltext
> search. All cheers to Jun and Bo I say! :-)
>
> I'll summarise what the current state is and what is planned to
> give a basis for discussion of how things could be integrated.
>
> Fulltext search separates indexing and searching.
>
> Indexing works like this: In couch.ini you specify a standalone
> daemon with the DbUpdateNotificationProcess setting. This
> daemon gets launched by CouchDB when it starts up. The
> daemon is supposed to listen on stdin for notifications
> from CouchDB.
>
> Each time a database in CouchDB is changed, CouchDB sends
> a JSON object over stdio to the notification daemon:
> {"type": "updated", "db":"database_name"}\n
> CouchDB expects no answer. The indexer can then do whatever
> he wants, for example polling CouchDB for the latest changes and
> save them into a fulltext index. The JSON structure might be
> expanded in the future, but in a backwards compatible
> manner (after 1.0, before 1.0 we might break everything :-).
>
> On this end, I think it would be nice to have a set of scripts that
> make it easy to register for events in all major languages so that
> people don't have to reimplement the listening and polling parts
> and concentrate on what they actually want to accomplish, but no
> design or work went into this direction.
>
>
> Searching works very similar in that a deamon listens on stdin
> for commands from CouchDB. The protocol is a little more complex
> here because it requires two-way communication.
> CouchDB exposes the search part over the HTTP API. At the
> moment you can call http://server:5984/database/_search?q="searchstring"
> and CouchDB will send this to the searcher daemon:
> database\n
> searchstring\n
> \n
> The searcher is expected to answer either with:
> error\n
> reason\n
> \n
>
> or
>
> ok\n
> docid\n
> score\n
> docid\n
> score\n
> .
> .
> .
> \n
>
> And CouchDB takes this list and returns it wrapped in JSON back to the
> caller.
>
> This is the state but I'd like to see some changes:
>
> I think we should move here from plaintext to JSON as well to gain a bit
> more flexibility. The basic idea is that this mechanism is good for
> any kind
> of indexing, not just fulltext. A friend of mine is already working on
> geo-
> searching with this interface[2]. (In this light, I propose drop the
> "fulltext" or
> "ft" label from the source for clarification).
>
> So we could handle calls like http://server:5984/database/_search?
> q="query"&some_custom_arg=value&other_arg=othervalue and pass it
> to the searcher API as:
> {"db":"database", "args":[{"q":"query"}, {"some_custom_arg":'value"},
> {"other_arg":"other_value'}]}\n
> \n
> and expect back a JSON result as well: either in single chunks or one
> huge object:
>
> Chunks:
> {"ok":"true"}\n (or {"error":"reason"`}\n\n)
> {"id":"docid", "score":"score"}\n
> {"id":"docid", "score":"score"}\n
> {"id":"docid", "score":"score"}\n
> ...
> \n
>
> Huge:
> {"ok":"true", result: [
> {"id":"docid", "score":"score"},
> {"id":"docid", "score":"score"},
> {"id":"docid", "score":"score"},
> ]}\n
> \n
>
> This would allow us to enable searchers to add custom values to the
> results
> and have CouchDB just add them transparently to the result set (like
> with the
> transparent handling of additional HTTP query arguments).
>
> All of those changes are just to explain the direction I wish to see
> this go in,
> no very well thought out proposals. I really appreciate your feedback
> and
> input here.
>
> I think we do have a halfway working indexer and searcher written for
> Java
> Lucene. I wrote some code for that a year ago and somebody (please
> step up!)
> improved that to work on the current CouchDB. But this certainly could
> use some
> work and any contributions here are very welcome (read: I don't want
> to do it).
>
> One more future direction that was discussed inconclusively before was
> the
> fulltext indexing of views. The general consensus was that we want to
> have it,
> but haven't figured out a good way to actually implement it. The
> mailing list
> archives have some valuable posts on that.
>
> So this is the current state. Now it's your turn :-)  How would
> JSearch fit into
> all this? I'm happy to help with any integration questions and
> suggestions for
> improvements on the CouchDB side, but I'd prefer not to have to deal
> with
> the Java side of things.
>
> Oh, and one more point Noah Slater brought up in IRC: Adding Java as a
> default requirement to CouchDB is quite heavy. And we need to discuss
> how this is supposed to be packaged and distributed with CouchDB.
>
> Cheers
> Jan
> --
>
> [1] I could swear there was a website but I can't find it anymore.
> So Jun an Bo, could you introduce JSearch to the others here?
>
> [2] http://vmx.cx/cgi-bin/blog/index.cgi

-- 
Søren Hilmer, M.Sc., M.Crypt.
wideTrail			Phone:	+45 25481225
Pilevænget 41		Email:	sh@widetrail.dk
DK-8961  Allingåbro	Web:	www.widetrail.dk

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