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From "Shai Erera (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3441) Add NRT support to LuceneTaxonomyReader
Date Tue, 20 Nov 2012 12:34:58 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3441?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13501141#comment-13501141
] 

Shai Erera commented on LUCENE-3441:
------------------------------------

bq. would the old TR ever receive a request to look up an out-of-bounds ord

In fact, it could. Like IR, the old TR still lives for old queries in flight. It is possible
that TR-1 received a FacetRequest with a category that it doesn't recognize, but because the
cache is now shared, and the TR-2 recognizes that category and put it in the cache, TR-1 will
receive its ordinal, which is out-of-bound.

Took a re-look at the code, and I think that it's solvable by having TR do a bounds check.
It is a very simple and cheap check, only one 'if', which will happen, in practice, only for
the top-K categories and the FacetRequest initially. I.e., the entire faceted search process
-- aggregating the categories, determining top-K etc., all happen on the ordinals that are
known to the search index (IR-1, that is coupled with TR-1).

In fact, the labeling that IR-1/TR-1 will do to the top-K cannot out-of-bound, so actually
only the FacetRequest may out-of-bound. Still, I think that it's safer to add the bounds check
to both caches.

I will post a new patch soon, compiled with the comments from Sivan (thanks !), and removing
the nocommit.
                
> Add NRT support to LuceneTaxonomyReader
> ---------------------------------------
>
>                 Key: LUCENE-3441
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3441
>             Project: Lucene - Core
>          Issue Type: New Feature
>          Components: modules/facet
>            Reporter: Shai Erera
>            Assignee: Shai Erera
>            Priority: Minor
>         Attachments: LUCENE-3441.patch
>
>
> Currently LuceneTaxonomyReader does not support NRT - i.e., on changes to LuceneTaxonomyWriter,
you cannot have the reader updated, like IndexReader/Writer. In order to do that we need to
do the following:
> # Add ctor to LuceneTaxonomyReader to allow you to instantiate it with LuceneTaxonomyWriter.
> # Add API to LuceneTaxonomyWriter to expose its internal IndexReader
> # Change LTR.refresh() to return an LTR, rather than void. This is actually not strictly
related to that issue, but since we'll need to modify refresh() impl, I think it'll be good
to change its API as well. Since all of facet API is @lucene.experimental, no backwards issues
here (and the sooner we do it, the better).

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