[jira] Commented: (LUCENE-767) maxDoc should be explicitly stored in the index, not derived from file length

["Chuck Williams (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-767?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12463322 ] 

Chuck Williams commented on LUCENE-767:
---------------------------------------

Isn't maxDoc always the same as the docCount of the segment, which is stored?  I.e., couldn't SegmentReader.maxDoc() be equivalently defined as:

  public int maxDoc() {
    return si.docCount;
  }

Since maxDoc==numDocs==docCount for a newly merged segment, and deletion with a reader never changes numDocs or maxDoc, it seems to me these values should always be the same.

All Lucene tests pass with this definition.  I have code that relies on this equivalence and so would appreciate knowledge of any case where this equivalence might not hold.


> maxDoc should be explicitly stored in the index, not derived from file length
> -----------------------------------------------------------------------------
>
>                 Key: LUCENE-767
>                 URL: https://issues.apache.org/jira/browse/LUCENE-767
>             Project: Lucene - Java
>          Issue Type: Improvement
>    Affects Versions: 1.9, 2.0.0, 2.0.1, 2.1
>            Reporter: Michael McCandless
>         Assigned To: Michael McCandless
>            Priority: Minor
>
> This is a spinoff of LUCENE-140
> In general we should rely on "as little as possible" from the file system.  Right now, maxDoc is derived by checking the file length of the FieldsReader index file (.fdx) which makes me nervous.  I think we should explicitly store it instead.
> Note that there are no known cases where this is actually causing a problem. There was some speculation in the discussion of LUCENE-140 that it could be one of the possible, but in digging / discussion there were no specifically relevant JVM bugs found (yet!).  So this would be a defensive fix at this point.

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