[jira] [Created] (LUCENE-7341) EarlyTerminatingSortingCollector support for grouped searches

["Christine Poerschke (JIRA)" <ji...@apache.org>]

Christine Poerschke created LUCENE-7341:
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             Summary: EarlyTerminatingSortingCollector support for grouped searches
                 Key: LUCENE-7341
                 URL: https://issues.apache.org/jira/browse/LUCENE-7341
             Project: Lucene - Core
          Issue Type: New Feature
            Reporter: Christine Poerschke
            Assignee: Christine Poerschke
            Priority: Minor


Currently grouped searches must not use the early terminating sorting collector because the wrong results would be returned. This ticket proposes to change the {{EarlyTerminatingSortingCollector}} class and probably the {{LeafCollector}} interface to support early termination for grouped searches.

*Illustration (aaa is an as yet unnamed boolean flag):*
{code}
# fictitious (sorted by X) segment
| doc key | D0 D1 D2 D3 D4 D5 ... D10 D11 D12 D13 D14 D15 ... D20 D21 D22 D23 D24 D25 ...
| doc grp | G0 G0 G0 G0 G0 G0 ... D10 G10 G10 G10 G10 G10 ... G20 G20 G20 G20 G20 G20 ... 
{code}

{code}
# query with rows=3 sort=X group=false
| query result | D0 D1 D2

# existing code:
#   use a EarlyTerminatingSortingCollector with numDocsToCollect=3
#   EarlyTerminatingSortingCollector.getLeafCollector returns a LeafCollector
#   whose collect method uses (++numCollected >= numDocsToCollect) as the terminating condition
{code}

{code}
# query with rows=3 sort=X group=true group.field=grp group.sort=X group.limit=1
| query result | G0(D0) G10(D10) G20(D20)

# existing code:
#   cannot use EarlyTerminatingSortingCollector (query result would wrongly be just 'G0(D0)')
# proposed new code:
#   use a EarlyTerminatingSortingCollector(... numDocsToCollect=3 aaa=true)
{code}

{code}
# query with rows=3 sort=X group=true group.field=grp group.sort=X group.limit=5
| query result | G0(D0,D1,D2,D3,D4) G10(D10,D11,D12,D13,D14) G20(D20,D21,D22,D23,D24)

# existing code:
#   cannot use EarlyTerminatingSortingCollector (query result would wrongly be just 'G0(D0,D1,D2)')
# proposed new code:
#   use a EarlyTerminatingSortingCollector(... numDocsToCollect=3 aaa=true)
{code} 



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