[jira] [Commented] (LUCENE-8292) Fix FilterLeafReader.FilterTermsEnum to delegate all seekExact methods

["David Smiley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-8292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16763797#comment-16763797 ] 

David Smiley commented on LUCENE-8292:
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Adrien last said:
{quote}In general, we do not delegate methods that have a default implementation because the default implementation is correct regardless of what the wrapper class does. Overriding these methods in FilterTermsEnum to delegate to the wrapped instance would make room for bugs by requiring more methods to be overridden for the wrapper to be correct.
{quote}
CC [~simonw] curious about your thoughts too

_In general_ I can see this.  For the case of termState() and seekExact(termState) in particular, I don't.  Hypothetically what could go wrong if FilterTermsEnum delegated?  When I think of filtering a TermsEnum, I think of something that might match a subset of terms from the underlying TermsEnum.  The TermsEnum must be positioned to something that matches when termState is called.  If seekExact(termState) in the underlying TermsEnum receives some termState impl it doesn't identify (isn't of a class it knows), then you get the default functional behavior, which is safe.  I'm looking at the 6 subclasses of FilterTermsEnum we have in Lucene and I don't see an issue.  (Interestingly, 3 of them are in the UnifiedHighlighter).  I checked that delegating these two methods doesn't result in test failures too, aside from TestFilterLeafReader.testOverrideMethods which expressly tests our policy.

> Fix FilterLeafReader.FilterTermsEnum to delegate all seekExact methods
> ----------------------------------------------------------------------
>
>                 Key: LUCENE-8292
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8292
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: core/index
>    Affects Versions: 7.2.1
>            Reporter: Bruno Roustant
>            Priority: Major
>             Fix For: trunk
>
>         Attachments: 0001-Fix-FilterLeafReader.FilterTermsEnum-to-delegate-see.patch, LUCENE-8292.patch
>
>
> FilterLeafReader#FilterTermsEnum wraps another TermsEnum and delegates many methods.
> It misses some seekExact() methods, thus it is not possible to the delegate to override these methods to have specific behavior (unlike the TermsEnum API which allows that).
> The fix is straightforward: simply override these seekExact() methods and delegate.



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