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https://issues.apache.org/jira/browse/LUCENE-8060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16558683#comment-16558683
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Adrien Grand commented on LUCENE-8060:
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{quote}why have a setDefaultNumTotalHitsToTrack(int) just for this concept, and
not a setter for all the other collector concepts that we currently have
defaults for in the simple search/searchAfter methods (like Sort sort , boolean
doDocScores , boolean doMaxScore , etc...)
{quote}
Actually some concepts like the similarity and the query cache policy are set
as members of IndexSearcher, so this isn't really new? I think the assumption
is that you most likely need the same values for most your requests and do not
need it to be configurable on a per-request basis, unlike the sort or the
number of hits to collect?
{quote}do we want to go down the route of an IndexSearcherConfig ?
{quote}
A user suggested adding this class last year: LUCENE-7902. I don't have a
strong opinion on this one besides keeping a simple IndexSearcher ctor that
only take a reader and has sensible defaults.
{quote}this seems like it introduces divergent "intermediate APIs" for users to
learn about that might frustrate them down the road...
{quote}
This is a good point. I also dislike a bit adding new setters/configuration
options if we can come up with a default value that is reasonable and should
work for most users, at least as long as their use-case remains simple. I'm
seeing pros and cons either way and I would probably be fine either way too.
Based on your comments I am getting the feeling that you are leaning towards to
exposing this configuration option, having a sensible default and pointing
users to creating collectors manually if they have more specific needs, do I
get it right?
> Enable top-docs collection optimizations by default
> ---------------------------------------------------
>
> Key: LUCENE-8060
> URL: https://issues.apache.org/jira/browse/LUCENE-8060
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Priority: Minor
> Fix For: master (8.0)
>
>
> We are getting optimizations when hit counts are not required (sorted
> indexes, MAXSCORE, short-circuiting of phrase queries) but our users won't
> benefit from them unless we disable exact hit counts by default or we require
> them to tell us whether hit counts are required.
> I think making hit counts approximate by default is going to be a bit trappy,
> so I'm rather leaning towards requiring users to tell us explicitly whether
> they need total hit counts. I can think of two ways to do that: either by
> passing a boolean to the IndexSearcher constructor or by adding a boolean to
> all methods that produce TopDocs instances. I like the latter better but I'm
> open to discussion or other ideas?
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