Class AbstractFirstPassGroupingCollector<GROUP_VALUE_TYPE>
- java.lang.Object
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- org.apache.lucene.search.Collector
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- org.apache.lucene.search.grouping.AbstractFirstPassGroupingCollector<GROUP_VALUE_TYPE>
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- Direct Known Subclasses:
TermFirstPassGroupingCollector
public abstract class AbstractFirstPassGroupingCollector<GROUP_VALUE_TYPE> extends Collector
FirstPassGroupingCollector is the first of two passes necessary to collect grouped hits. This pass gathers the top N sorted groups. Concrete subclasses define what a group is and how it is internally collected.See
org.apache.lucene.search.grouping
for more details including a full code example.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Constructor Summary
Constructors Constructor Description AbstractFirstPassGroupingCollector(Sort groupSort, int topNGroups)
Create the first pass collector.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description boolean
acceptsDocsOutOfOrder()
Returntrue
if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) toCollector.collect(int)
.void
collect(int doc)
Called once for every document matching a query, with the unbased document number.protected abstract GROUP_VALUE_TYPE
copyDocGroupValue(GROUP_VALUE_TYPE groupValue, GROUP_VALUE_TYPE reuse)
Returns a copy of the specified group value by creating a new instance and copying the value from the specified groupValue in the new instance.protected abstract GROUP_VALUE_TYPE
getDocGroupValue(int doc)
Returns the group value for the specified doc.Collection<SearchGroup<GROUP_VALUE_TYPE>>
getTopGroups(int groupOffset, boolean fillFields)
Returns top groups, starting from offset.void
setNextReader(IndexReader reader, int docBase)
Called before collecting from each IndexReader.void
setScorer(Scorer scorer)
Called before successive calls toCollector.collect(int)
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Constructor Detail
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AbstractFirstPassGroupingCollector
public AbstractFirstPassGroupingCollector(Sort groupSort, int topNGroups) throws IOException
Create the first pass collector.- Parameters:
groupSort
- TheSort
used to sort the groups. The top sorted document within each group according to groupSort, determines how that group sorts against other groups. This must be non-null, ie, if you want to groupSort by relevance use Sort.RELEVANCE.topNGroups
- How many top groups to keep.- Throws:
IOException
- If I/O related errors occur
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Method Detail
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getTopGroups
public Collection<SearchGroup<GROUP_VALUE_TYPE>> getTopGroups(int groupOffset, boolean fillFields)
Returns top groups, starting from offset. This may return null, if no groups were collected, or if the number of unique groups collected is <= offset.- Parameters:
groupOffset
- The offset in the collected groupsfillFields
- Whether to fill toSearchGroup.sortValues
- Returns:
- top groups, starting from offset
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setScorer
public void setScorer(Scorer scorer) throws IOException
Description copied from class:Collector
Called before successive calls toCollector.collect(int)
. Implementations that need the score of the current document (passed-in toCollector.collect(int)
), should save the passed-in Scorer and call scorer.score() when needed.- Specified by:
setScorer
in classCollector
- Throws:
IOException
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collect
public void collect(int doc) throws IOException
Description copied from class:Collector
Called once for every document matching a query, with the unbased document number.Note: This is called in an inner search loop. For good search performance, implementations of this method should not call
Searcher.doc(int)
orIndexReader.document(int)
on every hit. Doing so can slow searches by an order of magnitude or more.- Specified by:
collect
in classCollector
- Throws:
IOException
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acceptsDocsOutOfOrder
public boolean acceptsDocsOutOfOrder()
Description copied from class:Collector
Returntrue
if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) toCollector.collect(int)
.Most Lucene Query implementations will visit matching docIDs in order. However, some queries (currently limited to certain cases of
BooleanQuery
) can achieve faster searching if theCollector
allows them to deliver the docIDs out of order.Many collectors don't mind getting docIDs out of order, so it's important to return
true
here.- Specified by:
acceptsDocsOutOfOrder
in classCollector
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setNextReader
public void setNextReader(IndexReader reader, int docBase) throws IOException
Description copied from class:Collector
Called before collecting from each IndexReader. All doc ids inCollector.collect(int)
will correspond to reader. Add docBase to the current IndexReaders internal document id to re-base ids inCollector.collect(int)
.- Specified by:
setNextReader
in classCollector
- Parameters:
reader
- next IndexReader- Throws:
IOException
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getDocGroupValue
protected abstract GROUP_VALUE_TYPE getDocGroupValue(int doc)
Returns the group value for the specified doc.- Parameters:
doc
- The specified doc- Returns:
- the group value for the specified doc
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copyDocGroupValue
protected abstract GROUP_VALUE_TYPE copyDocGroupValue(GROUP_VALUE_TYPE groupValue, GROUP_VALUE_TYPE reuse)
Returns a copy of the specified group value by creating a new instance and copying the value from the specified groupValue in the new instance. Or optionally the reuse argument can be used to copy the group value in.- Parameters:
groupValue
- The group value to copyreuse
- Optionally a reuse instance to prevent a new instance creation- Returns:
- a copy of the specified group value
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