[
https://issues.apache.org/jira/browse/LUCENE-3102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13035285#comment-13035285
]
Michael McCandless commented on LUCENE-3102:
--------------------------------------------
Patch to allow no wrapped collector looks good! I wonder/hope hotspot can
realize those method calls are no-ops...
Maybe change TestGrouping to randomly use this ctor? Ie, randomly, you can use
caching collector (not wrapped), then call its replay method twice (once
against 1st pass, then against 2nd pass, collectors), and then assert results
like normal. This is also a good verification that replay works twice...
On the OBS, it makes me nervous to just always do this; I'd rather have it
cutover at some point? Or perhaps it's an expert optional arg to create,
whether it should back w/ OBS vs int[]?
Or, ideally... we make a bit set impl that does this all under the hood (uses
int[] when there are few docs, and "ugprades" to OBS once there are "enough" to
justify it...), then we can just use that bit set here.
> Few issues with CachingCollector
> --------------------------------
>
> Key: LUCENE-3102
> URL: https://issues.apache.org/jira/browse/LUCENE-3102
> Project: Lucene - Java
> Issue Type: Bug
> Components: core/search
> Reporter: Shai Erera
> Assignee: Shai Erera
> Priority: Minor
> Fix For: 3.2, 4.0
>
> Attachments: LUCENE-3102-factory.patch, LUCENE-3102-nowrap.patch,
> LUCENE-3102.patch, LUCENE-3102.patch
>
>
> CachingCollector (introduced in LUCENE-1421) has few issues:
> # Since the wrapped Collector may support out-of-order collection, the
> document IDs cached may be out-of-order (depends on the Query) and thus
> replay(Collector) will forward document IDs out-of-order to a Collector that
> may not support it.
> # It does not clear cachedScores + cachedSegs upon exceeding RAM limits
> # I think that instead of comparing curScores to null, in order to determine
> if scores are requested, we should have a specific boolean - for clarity
> # This check "if (base + nextLength > maxDocsToCache)" (line 168) can be
> relaxed? E.g., what if nextLength is, say, 512K, and I cannot satisfy the
> maxDocsToCache constraint, but if it was 10K I would? Wouldn't we still want
> to try and cache them?
> Also:
> * The TODO in line 64 (having Collector specify needsScores()) -- why do we
> need that if CachingCollector ctor already takes a boolean "cacheScores"? I
> think it's better defined explicitly than implicitly?
> * Let's introduce a factory method for creating a specialized version if
> scoring is requested / not (i.e., impl the TODO in line 189)
> * I think it's a useful collector, which stands on its own and not specific
> to grouping. Can we move it to core?
> * How about using OpenBitSet instead of int[] for doc IDs?
> ** If the number of hits is big, we'd gain some RAM back, and be able to
> cache more entries
> ** NOTE: OpenBitSet can only be used for in-order collection only. So we can
> use that if the wrapped Collector does not support out-of-order
> * Do you think we can modify this Collector to not necessarily wrap another
> Collector? We have such Collector which stores (in-memory) all matching doc
> IDs + scores (if required). Those are later fed into several processes that
> operate on them (e.g. fetch more info from the index etc.). I am thinking, we
> can make CachingCollector *optionally* wrap another Collector and then
> someone can reuse it by setting RAM limit to unlimited (we should have a
> constant for that) in order to simply collect all matching docs + scores.
> * I think a set of dedicated unit tests for this class alone would be good.
> That's it so far. Perhaps, if we do all of the above, more things will pop up.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
