Class ToParentBlockJoinCollector

Collects parent document hits for a Lucene.Net.Search.Query containing one more more BlockJoinQuery clauses, sorted by the specified parent Lucene.Net.Search.Sort. Note that this cannot perform arbitrary joins; rather, it requires that all joined documents are indexed as a doc block (using AddDocuments(IEnumerable<IEnumerable<IIndexableField>>, Analyzer) or UpdateDocuments(Term, IEnumerable<IEnumerable<IIndexableField>>, Analyzer). Ie, the join is computed at index time.

The parent Lucene.Net.Search.Sort must only use fields from the parent documents; sorting by field in the child documents is not supported.

You should only use this collector if one or more of the clauses in the query is a ToParentBlockJoinQuery. This collector will find those query clauses and record the matching child documents for the top scoring parent documents.

Multiple joins (star join) and nested joins and a mix of the two are allowed, as long as in all cases the documents corresponding to a single row of each joined parent table were indexed as a doc block.

For the simple star join you can retrieve the Lucene.Net.Search.Grouping.ITopGroups<TGroupValue> instance containing each ToParentBlockJoinQuery's matching child documents for the top parent groups, using GetTopGroups(ToParentBlockJoinQuery, Sort, Int32, Int32, Int32, Boolean). Ie, a single query, which will contain two or more ToParentBlockJoinQuery's as clauses representing the star join, can then retrieve two or more Lucene.Net.Search.Grouping.ITopGroups<TGroupValue> instances.

For nested joins, the query will run correctly (ie, match the right parent and child documents), however, because Lucene.Net.Search.Grouping.TopGroups<TGroupValue> is currently unable to support nesting (each group is not able to hold another Lucene.Net.Search.Grouping.TopGroups<TGroupValue>), you are only able to retrieve the Lucene.Net.Search.Grouping.TopGroups<TGroupValue> of the first join. The Lucene.Net.Search.Grouping.TopGroups<TGroupValue> of the nested joins will not be correct.

See http://lucene.apache.org/core/4_8_0/join/ for a code sample.

Note

This API is experimental and might change in incompatible ways in the next release.

Inheritance

System.Object

ToParentBlockJoinCollector

Implements

Lucene.Net.Search.ICollector

Inherited Members

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.ToString()

Namespace: Lucene.Net.Search.Join

Assembly: Lucene.Net.Join.dll

Syntax

public class ToParentBlockJoinCollector : ICollector

Constructors

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ToParentBlockJoinCollector(Sort, Int32, Boolean, Boolean)

Creates a ToParentBlockJoinCollector. The provided sort must not be null. If you pass true trackScores, all ToParentBlockQuery instances must not use None.

Declaration

public ToParentBlockJoinCollector(Sort sort, int numParentHits, bool trackScores, bool trackMaxScore)

Parameters

Type	Name	Description
Lucene.Net.Search.Sort	sort
System.Int32	numParentHits
System.Boolean	trackScores
System.Boolean	trackMaxScore

Properties

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AcceptsDocsOutOfOrder

Declaration

public virtual bool AcceptsDocsOutOfOrder { get; }

Property Value

Type	Description
System.Boolean

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MaxScore

Returns the highest score across all collected parent hits, as long as trackMaxScores=true was passed ToParentBlockJoinCollector(Sort, Int32, Boolean, Boolean) on construction. Else, this returns System.Single.NaN.

Declaration

public virtual float MaxScore { get; }

Property Value

Type	Description
System.Single

Methods

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Collect(Int32)

Declaration

public virtual void Collect(int parentDoc)

Parameters

Type	Name	Description
System.Int32	parentDoc

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GetTopGroups(ToParentBlockJoinQuery, Sort, Int32, Int32, Int32, Boolean)

Returns the Lucene.Net.Search.Grouping.ITopGroups<TGroupValue> for the specified BlockJoinQuery. The groupValue of each GroupDocs will be the parent docID for that group. The number of documents within each group is calculated as minimum of maxDocsPerGroup and number of matched child documents for that group. Returns null if no groups matched.

Declaration

public virtual ITopGroups<int> GetTopGroups(ToParentBlockJoinQuery query, Sort withinGroupSort, int offset, int maxDocsPerGroup, int withinGroupOffset, bool fillSortFields)

Parameters

Type	Name	Description
ToParentBlockJoinQuery	query	Search query
Lucene.Net.Search.Sort	withinGroupSort	Sort criteria within groups
System.Int32	offset	Parent docs offset
System.Int32	maxDocsPerGroup	Upper bound of documents per group number
System.Int32	withinGroupOffset	Offset within each group of child docs
System.Boolean	fillSortFields	Specifies whether to add sort fields or not

Returns

Type	Description
Lucene.Net.Search.Grouping.ITopGroups<System.Int32>	Lucene.Net.Search.Grouping.ITopGroups<TGroupValue> for specified query

Exceptions

Type	Condition
System.IO.IOException	if there is a low-level I/O error

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GetTopGroupsWithAllChildDocs(ToParentBlockJoinQuery, Sort, Int32, Int32, Boolean)

Returns the Lucene.Net.Search.Grouping.TopGroups<TGroupValue> for the specified BlockJoinQuery. The groupValue of each GroupDocs will be the parent docID for that group. The number of documents within each group equals to the total number of matched child documents for that group. Returns null if no groups matched.

Declaration

public virtual ITopGroups<int> GetTopGroupsWithAllChildDocs(ToParentBlockJoinQuery query, Sort withinGroupSort, int offset, int withinGroupOffset, bool fillSortFields)

Parameters

Type	Name	Description
ToParentBlockJoinQuery	query	Search query
Lucene.Net.Search.Sort	withinGroupSort	Sort criteria within groups
System.Int32	offset	Parent docs offset
System.Int32	withinGroupOffset	Offset within each group of child docs
System.Boolean	fillSortFields	Specifies whether to add sort fields or not

Returns

Type	Description
Lucene.Net.Search.Grouping.ITopGroups<System.Int32>	Lucene.Net.Search.Grouping.ITopGroups<TGroupValue> for specified query

Exceptions

Type	Condition
System.IO.IOException	if there is a low-level I/O error

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SetNextReader(AtomicReaderContext)

Declaration

public virtual void SetNextReader(AtomicReaderContext context)

Parameters

Type	Name	Description
Lucene.Net.Index.AtomicReaderContext	context

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SetScorer(Scorer)

Declaration

public virtual void SetScorer(Scorer scorer)

Parameters

Type	Name	Description
Lucene.Net.Search.Scorer	scorer

Implements

Lucene.Net.Search.ICollector