On Apr 15, 2008, at 02:01, Nils Adermann wrote:
Hi,
I agree with Søren that this is not necessarily a good idea. It is
not trivial for an indexer to figure out which view results changed.
One method to so is storing all indexed view results and then
comparing them to the updated view once the indexer is called. This
is a needless waste of resources. Updating the view index based on
changed documents is even more difficult. You would have to
recompute the view at least partially to find out which view results
changed. Given the reduce step this means that any number of
documents, including unchanged ones could be involved. This creates
a lot of work.
Yeah, but it doesn't actually matter who does the work :) So we rather
keep that out of CouchDB.
I think the problem we face here is different usage patterns of
views. There are views which process a lot of data and which are
based on documents that are updated frequently. But they might only
be read from infrequently. These views profit from JIT computation.
However many applications use views which are infrequently updated
but often queried or searched. Such views benefit from live
updating. If an application allows searching data it nearly always
means that the data will be read more frequently than it is updated.
So in conclusion both methods (JIT and live updates) make sense for
views. But search normally only needs the live update mechanism. I
believe it should become configurable whether a view is updated
immediately after a change or only after a query takes place.
Fulltext search would always work on views with immediate updates.
The indexer would be notified about the changed results. On views
which delay updates, search would only work if the fulltext search
provides a mechanism to compare the new view results to the old ones.
Just query the view with ?count=0 to trigger an update after your
inserts and you have the synchronous update behaviour.
Cheers
Nils
Jan Lehnardt wrote:
On Apr 12, 2008, at 12:06, Søren Hilmer wrote:
Hi
Have you read Chris' response about letting the view engine call
the indexer,
as it has the information needed for the indexer? As I understand
the idea,
it will essentially keep the fulltext indexer and the views in sync.
I like this idea and I believe the code for the indexer would be
much simpler
and efficient.
Also as the shift goes towards indexing views and not documents,
it makes
sense that it is the View engine that triggers the indexer, right?
The only problem here is that views are changed, when they are
being queried and not when documents are added. So you could end up
with a lot of not-indexed data because your view hasn't been
queried. That can be worked around, but I don't think it makes
things any easier :)
The design of the update notification is intentionally simple. We
expect the clients (the Indexer in this case) to be smart. We
believe that this makes the server code is more robust in that way.
I have to study the View engine, if I am to provide any code for
this, though
(provided consensus blows in this direction).
Have fun
Søren
On Friday 11 April 2008 13:26, Jan Lehnardt wrote:
On Apr 11, 2008, at 08:55, Søren Hilmer wrote:
Hi Jan
It certainly would simplify configuration, allthough the
DbUpdateNotificationProcess setting ought to be retained as it is
potentially usefull for other stuff than indexing (can you have
more
than
one of these, setup?)
No, the update searcher will stay! :-)
I am also worried about responsetimes for searching, potentially
the
indexing can take considerable time. With the current approach
indexing
can be done off peak hours and only searching is done at prime
time.
Right, if you want to be conservative with resources, you might
want
togo
with my approach at the expense of possibly higher response times
the
first time things are searched for (as it is with views). I just
wanted to make
available my idea that fulltext indexing could be modelled after
how
views
work, in case this is useful for a specific scenario.
Cheers
Jan
--
Have fun
Søren
--
Søren Hilmer, M.Sc., M.Crypt.
wideTrail Phone: +45 25481225
Pilevænget 41 Email: [EMAIL PROTECTED]
DK-8961 Allingåbro Web: www.widetrail.dk
On Thu, April 10, 2008 23:32, Jan Lehnardt wrote:
Heya,
while thinking more about the fulltext implementation, I began to
wonder why we don't model it after the view engine.
At the moment, we have an Indexer waiting for update
notifications
and
polling CouchDB for changes and a separate mechanism to
register a
fulltext query Searcher, that looks up things in the index.
My proposed architectural change would be to trigger the
Indexer from
the Searcher module when a request comes in, just like views
work.
This would delay the creation of fulltext indexes until they are
actually needed.
The possible drawback though is, that when building the fulltext
index
is rather slow, old-style pre-calculation might be more feasible.
View
deal with that by requiring frequent requests (possibly cron-ed).
This is not a proposal or anything, just a thought I wanted to
share
with those who work on fulltext integration.
If you have any input on this, please let us know ;)
Cheers
Jan
--
--
Søren Hilmer, M.Sc., M.Crypt.
wideTrail Phone: +45 25481225
Pilevænget 41 Email: [EMAIL PROTECTED]
DK-8961 Allingåbro Web: www.widetrail.dk
