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https://issues.apache.org/jira/browse/LUCENE-6826?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Trejkaz updated LUCENE-6826:
----------------------------
Attachment: Lucene6826.java
This test creates an index with one document which contains a value which does
not match the filter. It then migrates the index in a fashion that just filters
out the values, we don't want, which becomes all values in that field, which
triggers the error.
The first half of the day I tried to reproduce the exact same thing from
scratch with no success - it happily migrated. This version comes from working
code, simplified as far as possible without removing the issue, so it could
turn out that there is a subtle bug in my code as well.
> java.lang.ClassCastException: org.apache.lucene.index.TermsEnum$2 cannot be
> cast to org.apache.lucene.index.MultiTermsEnum when adding indexes
> ----------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: LUCENE-6826
> URL: https://issues.apache.org/jira/browse/LUCENE-6826
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/index
> Affects Versions: 5.2.1
> Reporter: Trejkaz
> Attachments: Lucene6826.java
>
>
> We are using addIndexes and FilterCodecReader tricks as part of index
> migration.
> Whether FilterCodecReader tricks are required to reproduce this is uncertain,
> but in any case, when migrating a particular index, I saw this exception:
> {noformat}
> java.lang.ClassCastException: org.apache.lucene.index.TermsEnum$2 cannot be
> cast to org.apache.lucene.index.MultiTermsEnum
> at
> org.apache.lucene.index.MappedMultiFields$MappedMultiTerms.iterator(MappedMultiFields.java:65)
> at
> org.apache.lucene.codecs.blocktree.BlockTreeTermsWriter.write(BlockTreeTermsWriter.java:426)
> at
> org.apache.lucene.codecs.perfield.PerFieldPostingsFormat$FieldsWriter.write(PerFieldPostingsFormat.java:198)
> at
> org.apache.lucene.codecs.FieldsConsumer.merge(FieldsConsumer.java:105)
> at
> org.apache.lucene.index.SegmentMerger.mergeTerms(SegmentMerger.java:193)
> at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:95)
> at org.apache.lucene.index.IndexWriter.addIndexes(IndexWriter.java:2519)
> {noformat}
> TermsEnum$2 appears to be TermsEnum.EMPTY. The place where it creates it is
> here:
> MultiTermsEnum#reset:
> {code}
> if (queue.size() == 0) {
> return TermsEnum.EMPTY; // <- this is not a MultiTermsEnum
> } else {
> return this;
> }
> {code}
> A quick hack would be for MappedMultiFields to check for TermsEnum.EMPTY
> specifically before casting, but there might be some way to avoid the cast
> entirely and that would obviously be a better idea.
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