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https://issues.apache.org/jira/browse/LUCENE-1727?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12726679#action_12726679
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Hoss Man commented on LUCENE-1727:
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bq. It's a good reminder to avoid documenting how something works as a
guarantee that it will always work that way.
I remember it being pretty heavily advertised as a feature for as long as i can
remember -- it was the entire basis for adding the FieldSelector API.
Based on McCandless comments in email, it sounds like order was only ever
maintained for fields that don't use term vectors -- in which case the
documentation was only ever partially correct. If it's possible to fix it to
work at least as well as it use to that seems worth while considering how much
FieldSelector depends on it.
(I admit however: it's kind of scary that it's been such an implicit assumption
but apparently never had a unit test)
> Order of stored Fields not maintained
> -------------------------------------
>
> Key: LUCENE-1727
> URL: https://issues.apache.org/jira/browse/LUCENE-1727
> Project: Lucene - Java
> Issue Type: Bug
> Components: Index
> Affects Versions: 2.4, 2.4.1
> Reporter: Hoss Man
> Assignee: Michael McCandless
> Fix For: 2.9
>
>
> As noted in these threads...
> http://www.nabble.com/Order-of-fields-returned-by-Document.getFields%28%29-to21034652.html
> http://www.nabble.com/Order-of-fields-within-a-Document-in-Lucene-2.4%2B-to24210597.html
> somewhere prior to Lucene 2.4.1 a change was introduced that prevents the
> Stored fields of a Document from being returned in same order that they were
> originally added in. This can cause serious performance problems for people
> attempting to use LoadFirstFieldSelector or a custom FieldSelector with the
> LOAD_AND_BREAK, or the SIZE_AND_BREAK options (since the fields don't come
> back in the order they expect)
> Speculation in the email threads is that the origin of this bug is code
> introduced by LUCENE-1301 -- but the purpose of that issue was refactoring,
> so if it really is the cause of the change this would seem to be a bug, and
> not a side affect of a conscious implementation change.
> Someone who understands indexing internals should investigate this. At a
> minimum, if it's decided that this is not actual a bug, then prior to
> resolving this bug the wiki docs and some of the FIeldSelector javadocs
> should be updated to make it clear what order Fields will be returned in.
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