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From "Murali Krishna P (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-7897) RangeQuery optimization in IndexOrDocValuesQuery
Date Thu, 03 Aug 2017 08:19:00 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-7897?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16112398#comment-16112398
] 

Murali Krishna P commented on LUCENE-7897:
------------------------------------------

Thanks Adrien for the patch. The changes look good from my perspective. However, it would
be better if someone who is more familiar with this part of the code also reviews it. For
example, I am not very sure about he opt() method where you removed the pq which was ordering
the optionalScorers in a particular way earlier.

Does the daily benchmark have the right dataset and query to track the improvement?

> RangeQuery optimization in IndexOrDocValuesQuery 
> -------------------------------------------------
>
>                 Key: LUCENE-7897
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7897
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: core/search
>    Affects Versions: trunk, 7.0
>            Reporter: Murali Krishna P
>         Attachments: LUCENE-7897.patch
>
>
> For range queries, Lucene uses either Points or Docvalues based on cost estimation (https://lucene.apache.org/core/6_5_0/core/org/apache/lucene/search/IndexOrDocValuesQuery.html).
Scorer is chosen based on the minCost here: https://github.com/apache/lucene-solr/blob/master/lucene/core/src/java/org/apache/lucene/search/Boolean2ScorerSupplier.java#L16
> However, the cost calculation for TermQuery and IndexOrDocvalueQuery seems to have same
weightage. Essentially, cost depends upon the docfreq in TermDict, number of points visited
and number of docvalues. In a situation where docfreq is not too restrictive, this is lot
of lookups for docvalues and using points would have been better.
> Following query with 1M matches, takes 60ms with docvalues, but only 27ms with points.
If I change the query to "message:*", which matches all docs, it choses the points(since cost
is same), but with message:xyz it choses docvalues eventhough doc frequency is 1million which
results in many docvalue fetches. Would it make sense to change the cost of docvalues query
to be higher or use points if the docfreq is too high for the term query(find an optimum threshold
where points cost < docvalue cost)?
> {noformat}
> {
>   "query": {
>     "bool": {
>       "must": [
>         {
>           "query_string": {
>             "query": "message:xyz"
>           }
>         },
>         {
>           "range": {
>             "@timestamp": {
>               "gte": 1498652400000,
>               "lte": 1498905000000,
>               "format": "epoch_millis"
>             }
>           }
>         }
>       ]
>     }
>   }
> }
> {noformat}



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