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From "Bruno Roustant (Jira)" <>
Subject [jira] [Commented] (LUCENE-8041) All Fields.terms(fld) impls should be O(1) not O(log(N))
Date Tue, 03 Dec 2019 09:56:00 GMT


Bruno Roustant commented on LUCENE-8041:

I created LUCENE-9078 "Term vectors options should not be configurable per-doc".

[~dsmiley] should we close this one?

> All Fields.terms(fld) impls should be O(1) not O(log(N))
> --------------------------------------------------------
>                 Key: LUCENE-8041
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: David Smiley
>            Priority: Major
>         Attachments: LUCENE-8041-LinkedHashMap.patch, LUCENE-8041.patch
> I've seen apps that have a good number of fields -- hundreds.  The O(log(N)) of TreeMap
definitely shows up in a profiler; sometimes 20% of search time, if I recall.  There are many
Field implementations that are impacted... in part because Fields is the base class of FieldsProducer.
> As an aside, I hope Fields to go away some day; FieldsProducer should be TermsProducer
and not have an iterator of fields. If DocValuesProducer doesn't have this then why should
the terms index part of our API have it?  If we did this then the issue here would be a simple
transition to a HashMap.
> Or maybe we can switch to HashMap and relax the definition of Fields.iterator to not
necessarily be sorted?
> Perhaps the fix can be a relatively simple conversion over to LinkedHashMap in many cases
if we can assume when we initialize these internal maps that we consume them in sorted order
to begin with.

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