i am currently happy with Lucene performance but i want to understand
and speedup further
by limiting the results concretely. So i still donot know why totalHits
and scoredocs report
different number of hits.
Best regards
On 6/8/21 2:52 AM, Baris Kazar wrote:
my worry is actually about the lucene's performance.
if lucene collects thousands of hits instead of actually n (<<< a
couple of 1000s) hits, then this creates performance issue.
ScoreDoc array is ok as i mentioned ie, it has size n.
i will check count api.
Best regards
------------------------------------------------------------------------
*From:* Adrien Grand <jpou...@gmail.com>
*Sent:* Tuesday, June 8, 2021 2:46 AM
*To:* Lucene Users Mailing List
*Cc:* Baris Kazar
*Subject:* Re: An interesting case
When you call IndexSearcher#search(Query query, int n), there are two
cases:
- either your query matches n hits or more, and the TopDocs object
will have a ScoreDoc[] array that contains the n best scoring hits
sorted by descending score,
- or your query matches less then n hits and then the TopDocs object
will have all matches in the ScoreDoc[] array, sorted by descending score.
In both cases, TopDocs#totalHits gives information about the total
number of matches of the query. On older versions of Lucene (<7.0)
this is an integer that is always accurate, while on more recent
versions of Lucene (>= 8.0) it is a lower bound of the total number of
matches. It typically returns the number of collected documents
indeed, though this is an implementation detail that might change in
the future.
If you want to count the number of matches of a Query precisely, you
can use IndexSearcher#count.
On Tue, Jun 8, 2021 at 7:51 AM <baris.ka...@oracle.com
<mailto:baris.ka...@oracle.com>> wrote:
https://stackoverflow.com/questions/50368313/relation-between-topdocs-totalhits-and-parameter-n-of-indexsearcher-search
<https://urldefense.com/v3/__https://stackoverflow.com/questions/50368313/relation-between-topdocs-totalhits-and-parameter-n-of-indexsearcher-search__;!!GqivPVa7Brio!JjLGw8TaYQcqSC7BtpPSZl5dl-WqgwwcgGFhOqHSUKIsCaTSNpoDvOJjq0BbkQhfpw$>
looks like someone else also had this problem, too.
Any suggestions please?
Best regards
On 6/8/21 1:36 AM, baris.ka...@oracle.com
<mailto:baris.ka...@oracle.com> wrote:
> Hi,-
>
> I use IndexSearcher.search API with two parameters like Query
and int
> number (i set as 20).
>
> However, when i look at the TopDocs object which is the result
of this
> above API call
>
> i see thousands of hits from totalhits. Is this inaccurate or
Lucene
> is doing actually search based on that many results?
>
> But when i iterate over result of above API call's scoreDocs
object i
> get int number of hits (ie, 20 hits).
>
>
> I am trying to find out why
org.apache.lucene.search.Topdocs.TotalHits
> report a number of collected results than
>
> the actual number of results. I see on the order of couple of
> thousands vs 20.
>
>
> Best regards
>
>
>
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--
Adrien
