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From "Thomas Mueller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-7109) rep:facet returns wrong results for complex queries
Date Fri, 05 Jan 2018 09:51:00 GMT

    [ https://issues.apache.org/jira/browse/OAK-7109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16312793#comment-16312793
] 

Thomas Mueller commented on OAK-7109:
-------------------------------------

[~catholicon] OK I see facets does not exactly match "group by" + "count". So, what if we
add a feature to aggregate the data from a "select [rep:facet(...)] ... UNION select [rep:facet(...)]
..." query? I believe aggregating that data in the query engine should be possible, as the
data format of the facet feature is known.

>> What if Lucene doesn't index all the constraints?
> fail such queries

Sounds good to me. I believe right now, if a query uses "select [rep:facet(...)]", then only
indexes that support that are used. If there is no index that supports facets, then the query
should fail with an exception (if that's not the case yet, we should probably add that). If
the Lucene index doesn't support some of the conditions, then it shouldn't return an index
plan. That should solve the problem with "union" queries as well.

> rep:facet returns wrong results for complex queries
> ---------------------------------------------------
>
>                 Key: OAK-7109
>                 URL: https://issues.apache.org/jira/browse/OAK-7109
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: lucene
>    Affects Versions: 1.6.7
>            Reporter: Dirk Rudolph
>              Labels: facet
>         Attachments: facetsInMultipleRoots.patch, restrictionPropagationTest.patch
>
>
> eComplex queries in that case are queries, which are passed to lucene not containing
all original constraints. For example queries with multiple path restrictions like:
> {code}
> select [rep:facet(simple/tags)] from [nt:base] as a where contains(a.[*], 'ipsum') and
(isdescendantnode(a,'/content1') or isdescendantnode(a,'/content2'))
> {code}
> In that particular case the index planer gives ":fulltext:ipsum" to lucene even though
the index supports evaluating path constraints. 
> As counting the facets happens on the raw result of lucene, the returned facets are incorrect.
For example having the following content 
> {code}
> /content1/test/foo
>  + text = lorem ipsum
>  - simple/
>   + tags = tag1, tag2
> /content2/test/bar
>  + text = lorem ipsum
>  - simple/
>   + tags = tag1, tag2
> /content3/test/bar
>  + text = lorem ipsum
>  - simple/
>    + tags = tag1, tag2
> {code}
> the expected result for the dimensions of simple/tags and the query above is 
> - tag1: 2
> - tag2: 2
> as the result set is 2 results long and all documents are equal. The actual result set
is 
> - tag1: 3
> - tag2: 3
> as the path constraint is not handled by lucene.
> To workaround that the only solution that came to my mind is building the [disjunctive
normal form|https://en.wikipedia.org/wiki/Disjunctive_normal_form] of my complex query and
executing a query for each of the disjunctive statements. As this is expanding exponentially
its only a theoretical solution, nothing for production. 



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