This should probably be called FilterWeight to be consistent with the rest of the code base? Also, why does its constructor take a Query object too? I think it should only take a Weight object and use the query returned by Weight.getQuery() to pass to the parent constructor? Otherwise +1.

Thanks Adrien Grand for the quick review! Added extra constructor

protected FilterWeight(Weight weight) {
  super(weight.getQuery());
  this.in = weight;
}

as you suggested. It seems though that the FilterWeight(Query query, Weight weight) constructor variant is still needed to cater for BlockJoinWeight and ToChildBlockJoinWeight usage?

+1 nice. Remember to add at least a one liner javadoc at the class level; precommit will complain if you don't.

Oh, one more thing – make FilterWeight abstract to clarify it's use.

Thanks David Smiley for your comments, both included in revised patch.

Can you add @lucene.internal to the class javadocs and add a comment to the constructor that takes a Query parameter to be explicit about the fact that this query should be rewritten? Otherwise +1 to push.

Can you add @lucene.internal to the class javadocs ...

Just to confirm, @lucene.internal or @lucene.experimental or perhaps both?

I notice that FilterCollector and FilterLeafCollector are marked @lucene.experimental but other org.apache.lucene.search Filter classes are unmarked.

Should they (FilteredDocIdSetIterator, FilterScorer, FilterSpans) be marked also and if so (outside the scope of this ticket) as what?

Similar question would apply to org.apache.lucene.index Filter classes e.g. FilterCodecReader, FilterDirectoryReader, FilteredTermsEnum, FilterLeafReader and possibly other classes too.

Building your own query/weight is expert, so I'm more in favour of internal. While we want the API to consume queries to be stable, since this is what Lucene is about, I don't see it as a goal as far as implementing custom queries/weights is concerned.

Regarding the other Filter* classes, the annotation is indeed not used consistently. See also this comment: https://issues.apache.org/jira/browse/LUCENE-7123?focusedCommentId=15204103&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15204103.

• rebased for LUCENE-7368 changes and conflicts resolved
• @lucene.internal annotation
• javadocs for the two constructors

+1

Commit 15e8719b8aa80b1e7e8deeba6bf8bec99f663ac8 in lucene-solr's branch refs/heads/master from Christine Poerschke
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=15e8719 ]

LUCENE-7372: Factor out an org.apache.lucene.search.FilterWeight class.

Commit 625979113f8f1c5e33ed342645aff0594245ca46 in lucene-solr's branch refs/heads/branch_6x from Christine Poerschke
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=6259791 ]

LUCENE-7372: Factor out an org.apache.lucene.search.FilterWeight class.

Commit 5c178196184f2bd0e57da510869e44d3177ac679 in lucene-solr's branch refs/heads/branch_5x from Christine Poerschke
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=5c17819 ]

LUCENE-7372: Add org.apache.lucene.search.FilterWeight class + test.

(This adds the class and test only, as a partial cherry-pick of the branch_5x commit.)