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https://issues.apache.org/jira/browse/LUCENE-2335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12848380#action_12848380
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Michael McCandless commented on LUCENE-2335:
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bq. The sort-first-then-resolve-Strings is what I did in the proof of concept.
The speed is that of TermsInfoReader, where it delivers a Term from a given
position. If this is too slow for multiple segments, the segment-spanning
ordered ordinals-approach could be tried.
I fear both approaches are too slow. (This is why we have the
per-docXfield String values RAM resident now).
bq. As for deprecating stored fields, then I guess there's the issue of spatial
locality. Wouldn't moving the bytes into the inverted term index bloat it in a
way that makes all searches slower?
We're not planning on deprecating stored fields?
bq. There's an issue of having multiple terms in the same field for a given
document, which also ties into facets.
For sorting it must be a single term right?
Also, for facets, you have to visit all docs, aggregating, not just
the final top N in the queue?
Facets are fun to discuss... but let's keep this issue focused on how
to optimize the single-segment sorting case with fillFields=false.
> optimization: when sorting by field, if index has one segment and field
> values are not needed, do not load String[] into field cache
> ------------------------------------------------------------------------------------------------------------------------------------
>
> Key: LUCENE-2335
> URL: https://issues.apache.org/jira/browse/LUCENE-2335
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Michael McCandless
> Priority: Minor
> Fix For: 3.1
>
>
> Spinoff from java-dev thread "Sorting with little memory: A suggestion",
> started by Toke Eskildsen.
> When sorting by SortField.STRING we currently ask FieldCache for a
> StringIndex on that field.
> This can consumes tons of RAM, when the values are mostly unique (eg a title
> field), as it populates both int[] ords as well as String[] values.
> But, if the index is only one segment, and the search sets fillFields=false,
> we don't need the String[] values, just the int[] ords. If the app needs to
> show the fields it can pull them (for the 1 page) from stored fields.
> This can be a potent optimization -- alot of RAM saved -- for optimized
> indexes.
> When fixing this we must take care to share the int[] ords if some queries do
> fillFields=true and some =false... ie, FieldCache will be called twice and it
> should share the int[] ords across those invocations.
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