Class ToParentBlockJoinCollector

Collects parent document hits for a containing one more more BlockJoinQuery clauses, sorted by the specified parent . Note that this cannot perform arbitrary joins; rather, it requires that all joined documents are indexed as a doc block (using or . Ie, the join is computed at index time.

The parent 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 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 ITopGroups<TGroupValue> instances.

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

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

This is a Lucene.NET EXPERIMENTAL API, use at your own risk

Inheritance

System.Object

ToParentBlockJoinCollector

Namespace: Lucene.Net.Join

Assembly: Lucene.Net.Join.dll

Syntax

public class ToParentBlockJoinCollector : ICollector

Constructors

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
Sort	sort
System.Int32	numParentHits
System.Boolean	trackScores
System.Boolean	trackMaxScore

Properties

AcceptsDocsOutOfOrder

Declaration

public virtual bool AcceptsDocsOutOfOrder { get; }

Property Value

Type	Description
System.Boolean

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 .

Declaration

public virtual float MaxScore { get; }

Property Value

Type	Description
System.Single

Methods

Collect(Int32)

Declaration

public virtual void Collect(int parentDoc)

Parameters

Type	Name	Description
System.Int32	parentDoc

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

Returns the 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
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
ITopGroups<System.Int32>	ITopGroups<TGroupValue> for specified query

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

Returns the 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
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
ITopGroups<System.Int32>	ITopGroups<TGroupValue> for specified query

SetNextReader(AtomicReaderContext)

Declaration

public virtual void SetNextReader(AtomicReaderContext context)

Parameters

Type	Name	Description
AtomicReaderContext	context

SetScorer(Scorer)

Declaration

public virtual void SetScorer(Scorer scorer)

Parameters

Type	Name	Description
Scorer	scorer