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https://issues.apache.org/jira/browse/LUCENE-8060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16556268#comment-16556268
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Hoss Man commented on LUCENE-8060:
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{quote}I think as long as totalHits is renamed/replaced to force a compilation
error and draw attention to the need to use a Collector if you want to control
if/how-much the total number of hits is accurately recorded, it's fine to
hadcode a default in the IndexSearcher methods that return TopDocs directly ...
i would go so far as to suggest that in that in that situation, hardcoding
maxTotalHits/minExactTotalHits to "0" (ie: don't bother trying to track exactly
at all) would be fine.
{quote}
To elaborate, my thinking is that having the "simple" IndexSearcher APIs use a
default of "nothing" (or "everything", ie:
{{maxTotalHitsToTrack=Integer.MAX_VALUE}} ) seems much easier to
explain/understand to new users regardless of their index size/usecases then
some arbitrary positive number like "10,000")
But better still – let's assume:
* we deprecate/remove {{TopDocs.totalHits}}
** replace it with a {{TopDocs.getTotalHits()}}
* we add an {{int maxTotalHitsToTrack}} option on the collectors (builders)
** document it such that any positive number means "track accurate hit count
up to this amount, after that just stop"
** document everything such that if {{maxTotalHitsToTrack}} is set to a
negative number then then {{TopDocs.getTotalHits()}} will throw an illegal
state exception.
...then i would suggest that the IndexSearcher methods that return TopDocs
directly should default to using {{maxTotalHitsToTrack=-1}} .. so any attempt
to use the "simple" apis makes it really clear it doesn't support hit tracking.
> Require users to tell us whether they need total hit counts
> -----------------------------------------------------------
>
> 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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