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https://issues.apache.org/jira/browse/LUCENE-3041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13025283#comment-13025283
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Simon Willnauer commented on LUCENE-3041:
-----------------------------------------
{quote}
I don't quite follow you. Currently DispatchingQueryProcessor caches
InvocationDispatchers by concrete impl type. So we only create a new
InvocationDispatcher when we have a new implementation (which means
InvocationDispatchers are shared between segments, searches, everything). In
that regard DispatchingQueryProcessor#dispatcherByClass should be a
ConcurrentHashMap. But otherwise, I think we're okay?
{quote}
my bad.. I didn't look close enough :) Yet, I was proposing something like what
you did though :) the problem here could be that it is static but for now
ConcurrentHashMap would do.
bq.Any thoughts on how to avoid that?
hmm, I think we should try to dispatch first. If there is not specialized
method to dispatch we should rewrite and continue.
I still wonder how this would walk down the query tree so I am happily waiting
for the next patch.
> Support Query Visting / Walking
> -------------------------------
>
> Key: LUCENE-3041
> URL: https://issues.apache.org/jira/browse/LUCENE-3041
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Chris Male
> Priority: Minor
> Attachments: LUCENE-3041.patch
>
>
> Out of the discussion in LUCENE-2868, it could be useful to add a generic
> Query Visitor / Walker that could be used for more advanced rewriting,
> optimizations or anything that requires state to be stored as each Query is
> visited.
> We could keep the interface very simple:
> {code}
> public interface QueryVisitor {
> Query visit(Query query);
> }
> {code}
> and then use a reflection based visitor like Earwin suggested, which would
> allow implementators to provide visit methods for just Querys that they are
> interested in.
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