[jira] Commented: (LUCENE-762) [PATCH] Efficiently retrieve sizes of field values

["Grant Ingersoll (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12469326 ] 

Grant Ingersoll commented on LUCENE-762:
----------------------------------------

I agree, Chuck, I sometimes wish you could have JAR level access or something like that.  Off topic, but doesn't C++ have a friend operator (not that I'm wishing for the C++ days) that lets you do these kind of things.

I originally put FieldSelector in the Document package b/c I felt it was more closely associated with Documents and Fields than the Index package.  Now, I guess, since the FieldsReader is in Index, I can see a strong argument for that location.

Anyway, I thought of an alternative that should keep everyone happy:
Create a new Interface named FieldInfoAccessor which provides get methods for the properties on FieldInfo, which will implement the interface.  Pass that to FieldSelectorResult.readField method instead of FieldInfo and proceed as stated above.  

The only sticking point I am now having is what to do with the Lazy Fields, since they require the ThreadLocal in FieldsReader.  I guess I would have to pass in the cloneable Fields Reader and the threadlocal, but that doesn't seem quite right either.  Any thoughts?  Moving the FieldSelector stuff into index package wouldn't address this, I don't think.  Maybe a brilliant thought will occur to me in the morning.

> [PATCH] Efficiently retrieve sizes of field values
> --------------------------------------------------
>
>                 Key: LUCENE-762
>                 URL: https://issues.apache.org/jira/browse/LUCENE-762
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Store
>    Affects Versions: 2.1
>            Reporter: Chuck Williams
>         Assigned To: Grant Ingersoll
>            Priority: Minor
>         Attachments: SizeFieldSelector.patch
>
>
> Sometimes an application would like to know how large a document is before retrieving it.  This can be important for memory management or choosing between algorithms, especially in cases where documents might be very large.
> This patch extends the existing FieldSelector mechanism with two new FieldSelectorResults:  SIZE and SIZE_AND_BREAK.  SIZE creates fields on the retrieved document that store field sizes instead of actual values.  SIZE_AND_BREAK is especially efficient if one field comprises the bulk of the document size (e.g., the body field) and can thus be used as a reasonable size approximation.

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