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https://issues.apache.org/jira/browse/LUCENE-8610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16722043#comment-16722043
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Michael Gibney commented on LUCENE-8610:
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Changed to "minor wish"; this patch still might be a good idea, but I
encountered it in practice because I was using
{{solr.PreAnalyzedField$PreAnalyzedTokenizer}} incorrectly.
{{PreAnalyzedTokenizer}} (and its token Attributes) is not designed to be
reused _at all_ at index time. Caching concerns only apply to TokenStream
reuse, so now that I've corrected my use of {{PreAnalyzedTokenizer}}, this
patch could be viewed as a solution in search of a problem.
If this patch still has any merit, it would be because:
1. there might be TokenStreams that lazily instantiate token Attributes and
_are_ reused, or
2. this change would be a prerequisite for potentially modifying
{{PreAnalyzedTokenizer}} to enable reuse, thus avoiding creation of a
{{PreAnalyzedTokenizer}} (and all associated token Attributes) for every field
value.
I'm fine with just closing this issue; but again it's a pretty minor change
that won't hurt anything, and could in some cases make indexing more robust. Or
at least clarify whether it's acceptable for index-time TokenStreams to lazily
instantiate token Attributes ...
> NPE in TermsHashPerField.add() for TokenStreams with lazily instantiated
> token Attributes
> -----------------------------------------------------------------------------------------
>
> Key: LUCENE-8610
> URL: https://issues.apache.org/jira/browse/LUCENE-8610
> Project: Lucene - Core
> Issue Type: Wish
> Components: core/index
> Affects Versions: 7.4, master (8.0)
> Reporter: Michael Gibney
> Priority: Minor
> Attachments: LUCENE-8610.patch
>
>
> {{DefaultIndexingChain.invert(...)}} calls
> {{invertState.setAttributeSource(stream)}} before {{stream.incrementToken()}}
> is called.
> For instances of {{stream}} that lazily instantiate token attributes (e.g.,
> as {{solr.PreAnalyzedField$PreAnalyzedTokenizer}} does upon the first call to
> {{incrementToken()}} that returns {{true}}), this can result in caching a
> {{null}} value in {{invertState.termAttribute}} for a given {{stream}}
> instance.
> Subsequent calls that reuse the same {{stream}} instance (reusing
> {{TokenStreamComponents}}) for field values with at least 1 token will call
> {{termHashPerField.start(...)}} which sets {{termsHashPerField.termAtt}} from
> the {{null}} value cached in the {{FieldInvertState.termAttribute}}. An NPE
> is thrown when {{termsHashPerField.add()}} reasonably but incorrectly assumes
> a non-null value for {{termAtt}}.
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