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From "Adrien Grand (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (LUCENE-7897) RangeQuery optimization in IndexOrDocValuesQuery
Date Tue, 01 Aug 2017 13:38:00 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-7897?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Adrien Grand updated LUCENE-7897:
---------------------------------
    Attachment: LUCENE-7897.patch

I tried to implement some of your ideas:
 - The {{boolean randomAccess}} parameter has been replaced with {{long leadCost}} which gives
the cost of the scorer that will be used to lead iteration. This way we could move the decision
making of whether the query should run with points or doc values from {{Boolean2ScorerSupplier}}
to {{IndexOrDocValuesQuery}}.
 - The cost of {{IndexOrDocValuesQuery}} is now the cost of the wrapped {{indexQuery}}, it
ignores the doc values query.
 - I gave doc values queries an arbitrary 8x penalty, meaning that when intersecting a term
query with a range query, we will only use doc values for the range if it seems to match more
than 8x more documents than the term query (vs. 1x before this patch).

I had not though about it before writing this patch, but it should also make the situation
better for disjunctions in conjunctions, since the sparse clauses will now use sequential
access, reducing balancing operations on the priority queue.

> 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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