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https://issues.apache.org/jira/browse/LUCENE-1630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12720477#action_12720477
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Shai Erera commented on LUCENE-1630:
------------------------------------
Thanks for the review Mike. Answers below. The comments which I did not answer
will be fixed.
bq. Can we make Collector.supportsDocsOutOfOrder abstract? Defaulting to false
isn't great (I'd rather subclass think about the question).
In general, I tried to avoid it since that would require changing all core
Collectors. There aren't many, but still ...
This goes for QueryWeight.scoresOutOfOrder - wanted to avoid changing all core
Weights to impl the method w/ "return false". I actually think that many
Weights/Scorers do score documents in-order, hence the default impl.
bq. If a given Scorer.scoresOutOfOrder returns true, does that mean nextDoc is
allowed to return docs out of order?
When you deal with a Scorer which returns out-of-order, you can only call
scorer.score(Collector). If you're going to iterate, you're going to have to
create a Scorer in-order, and that's what IndexSearcher does. I'll spell it out
clearly in the javadocs.
bq. Should scoresOutOfOrder() move from QueryWeight --> Scorer?
We've discussed it few posts up. When this information in in Scorer, I should
first ask for a Scorer, and only then I can create a Collector. If I'll use the
Scorer immediately, then that'll be ok. However, that's not the case in
IndexSearcher, and results in a bug in Spatial, and unless we want to uglify
IndexSearcher code, it seemed that this can sit in QueryWeight.
But I do think it's a problematic method in QW too, since if it returns false
by default, I'll create a Collector which expects docs in-order, but then I'd
lose the optimization in BooleanWeight which may return an out-of-order
superior Scorer. If I return true, I'll create a Collector which expects
out-of-order, and the Scorer (again, an example from BW) may be actually
in-order, and I've wasted unnecessary 'if doc > topDoc' cycles.
So I don't know what's better: make IndexSearcher code more complicated or
sacrifice a potential loss of this optimization?
bq. Actually I think the way to factor the static setting in is backwards?
Shouldn't it be scoreDocsInOrder |= !allowDocsOutOfOrder?
Yes, nice catch :)
bq. Shouldn't Searchable cutover to QueryWeight too? (We are keeping
Searchable, but allowing changes to it)
I wrote that above too - I don't think we can declare and execute right in 2.9
that Searchable can be changed unexpectedly. So I added a NOTE to its javadocs
and thought to do the change post 2.9, when we remove Weight. We'd be forced to
change these methods to QueryWeight, and fix RemoteSearchable too. And it will
be consistent w/ our back-compat policy (at least the part where we declare on
an upcoming change before it happens).
But if you think otherwise, I don't mind deprecating and adding new methods
(I've got used to it already, I almost do it blindly :) ).
I'll fix the other comments, and post a patch back after we resolve the
remaining open issues.
> Mating Collector and Scorer on doc Id orderness
> -----------------------------------------------
>
> Key: LUCENE-1630
> URL: https://issues.apache.org/jira/browse/LUCENE-1630
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Shai Erera
> Assignee: Michael McCandless
> Fix For: 2.9
>
> Attachments: LUCENE-1630.patch, LUCENE-1630.patch
>
>
> This is a spin off of LUCENE-1593. This issue proposes to expose appropriate
> API on Scorer and Collector such that one can create an optimized Collector
> based on a given Scorer's doc-id orderness and vice versa. Copied from
> LUCENE-1593, here is the list of changes:
> # Deprecate Weight and create QueryWeight (abstract class) with a new
> scorer(reader, scoreDocsInOrder), replacing the current scorer(reader)
> method. QueryWeight implements Weight, while score(reader) calls
> score(reader, false /* out-of-order */) and scorer(reader, scoreDocsInOrder)
> is defined abstract.
> #* Also add QueryWeightWrapper to wrap a given Weight implementation. This
> one will also be deprecated, as well as package-private.
> #* Add to Query variants of createWeight and weight which return QueryWeight.
> For now, I prefer to add a default impl which wraps the Weight variant
> instead of overriding in all Query extensions, and in 3.0 when we remove the
> Weight variants - override in all extending classes.
> # Add to Scorer isOutOfOrder with a default to false, and override in BS to
> true.
> # Modify BooleanWeight to extend QueryWeight and implement the new scorer
> method to return BS2 or BS based on the number of required scorers and
> setAllowOutOfOrder.
> # Add to Collector an abstract _acceptsDocsOutOfOrder_ which returns
> true/false.
> #* Use it in IndexSearcher.search methods, that accept a Collector, in order
> to create the appropriate Scorer, using the new QueryWeight.
> #* Provide a static create method to TFC and TSDC which accept this as an
> argument and creates the proper instance.
> #* Wherever we create a Collector (TSDC or TFC), always ask for out-of-order
> Scorer and check on the resulting Scorer isOutOfOrder(), so that we can
> create the optimized Collector instance.
> # Modify IndexSearcher to use all of the above logic.
> The only class I'm worried about, and would like to verify with you, is
> Searchable. If we want to deprecate all the search methods on IndexSearcher,
> Searcher and Searchable which accept Weight and add new ones which accept
> QueryWeight, we must do the following:
> * Deprecate Searchable in favor of Searcher.
> * Add to Searcher the new QueryWeight variants. Here we have two choices: (1)
> break back-compat and add them as abstract (like we've done with the new
> Collector method) or (2) add them with a default impl to call the Weight
> versions, documenting these will become abstract in 3.0.
> * Have Searcher extend UnicastRemoteObject and have RemoteSearchable extend
> Searcher. That's the part I'm a little bit worried about - Searchable
> implements java.rmi.Remote, which means there could be an implementation out
> there which implements Searchable and extends something different than
> UnicastRemoteObject, like Activeable. I think there is very small chance this
> has actually happened, but would like to confirm with you guys first.
> * Add a deprecated, package-private, SearchableWrapper which extends Searcher
> and delegates all calls to the Searchable member.
> * Deprecate all uses of Searchable and add Searcher instead, defaulting the
> old ones to use SearchableWrapper.
> * Make all the necessary changes to IndexSearcher, MultiSearcher etc.
> regarding overriding these new methods.
> One other optimization that was discussed in LUCENE-1593 is to expose a
> topScorer() API (on Weight) which returns a Scorer that its score(Collector)
> will be called, and additionally add a start() method to DISI. That will
> allow Scorers to initialize either on start() or score(Collector). This was
> proposed mainly because of BS and BS2 which check if they are initialized in
> every call to next(), skipTo() and score(). Personally I prefer to see that
> in a separate issue, following that one (as it might add methods to
> QueryWeight).
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