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From "Jack Krupansky" <>
Subject Re: Lucene3xCodec doesn't allow deletions in 4x?
Date Wed, 29 Aug 2012 14:24:29 GMT
The current (4.0-BETA) CHANGES.txt does say the following:

"Mixed flex/pre-flex indexes are perfectly fine -- the two
    emulation layers (flex API on pre-flex index, and pre-flex API on
    flex index) will remap the access as required.  So on upgrading to
    4.0 you can start indexing new documents into an existing index."

I don't know if that was worded very carefully or sloppily, but some users 
may not be able to easily and quickly fathom the now-apparent restrictions 
hidden behind "Mixed flex/pre-flex indexes are perfectly fine." If the 
intention of the statement is to indicate that deletes and updates are not 
guaranteed, it should say so. I mean, "will remap the access as required" 
sounds as if ALL accesses will be remapped as required.

Granted, "indexing new documents" doesn't necessarily imply that modifying 
existing documents or deleting existing documents is supported, but it 
doesn't do anything to highlight these current limitations either, and 
average users should be excused for not parsing the statement so carefully.

Oh, and that text does fall under the header of "Changes in backwards 
compatibility policy" - suggesting that backwards compatibility policy has 
changed, although it is not clear from the language of the header whether 
this is simply a "limited, one-time special" policy change rather than a 
"general" policy change. The specific statements are clear about this being 
4.0, though. Actually, that "header" is not specific to the flex/codec 
change, which adds to the confusion.

I'm not going to strenuously argue that full back compat from 3.x to 4.x is 
a 100% requirement, but simply that the compatibility/upgrade statement be 
100% accurate and easy for non-committers to fathom.

-- Jack Krupansky

-----Original Message----- 
From: Robert Muir
Sent: Wednesday, August 29, 2012 7:59 AM
Subject: Re: Lucene3xCodec doesn't allow deletions in 4x?

On Wed, Aug 29, 2012 at 6:48 AM, Michael McCandless
<> wrote:
> I think it makes sense to allow deletions against 3.x segments?
> This has always been part of our index back-compat promise.  Ie, as
> long as all segments were written with version N-1, in version N of
> Lucene you can open up the index and do anything (searching,
> adding/updating/deleting docs, etc.) with it.

Where exactly? I only see that indexes should be read. In my opinion
the current codebase meets this requirement.

"Version X.N should be able to read indexes generated by any version
after and including version X-1.0, but may-or-may-not be able to read
indexes generated by version X-2.N. "


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