Class FieldMaskingSpanQuery

Wrapper to allow SpanQuery objects participate in composite single-field SpanQueries by 'lying' about their search field. That is, the masked SpanQuery will function as normal, but Field simply hands back the value supplied in this class's constructor.

This can be used to support Queries like SpanNearQuery or SpanOrQuery across different fields, which is not ordinarily permitted.

This can be useful for denormalized relational data: for example, when indexing a document with conceptually many 'children':

teacherid: 1
studentfirstname: james
studentsurname: jones
teacherid: 2
studenfirstname: james
studentsurname: smith
studentfirstname: sally
studentsurname: jones

A SpanNearQuery with a slop of 0 can be applied across two SpanTermQuery objects as follows:

SpanQuery q1  = new SpanTermQuery(new Term("studentfirstname", "james"));
 SpanQuery q2  = new SpanTermQuery(new Term("studentsurname", "jones"));
 SpanQuery q2m = new FieldMaskingSpanQuery(q2, "studentfirstname");
 Query q = new SpanNearQuery(new SpanQuery[] { q1, q2m }, -1, false);

to search for 'studentfirstname:james studentsurname:jones' and find teacherid 1 without matching teacherid 2 (which has a 'james' in position 0 and 'jones' in position 1).

Note: as Field returns the masked field, scoring will be done using the Similarity and collection statistics of the field name supplied, but with the term statistics of the real field. This may lead to exceptions, poor performance, and unexpected scoring behavior.

Inheritance

object

Query

SpanQuery

FieldMaskingSpanQuery

Inherited Members

Query.Boost

Query.ToString()

Query.Clone()

object.Equals(object, object)

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Search.Spans

Assembly: Lucene.Net.dll

Syntax

public class FieldMaskingSpanQuery : SpanQuery

Constructors

FieldMaskingSpanQuery(SpanQuery, string)

Wrapper to allow SpanQuery objects participate in composite single-field SpanQueries by 'lying' about their search field. That is, the masked SpanQuery will function as normal, but Field simply hands back the value supplied in this class's constructor.

This can be used to support Queries like SpanNearQuery or SpanOrQuery across different fields, which is not ordinarily permitted.

This can be useful for denormalized relational data: for example, when indexing a document with conceptually many 'children':

teacherid: 1
studentfirstname: james
studentsurname: jones
teacherid: 2
studenfirstname: james
studentsurname: smith
studentfirstname: sally
studentsurname: jones

A SpanNearQuery with a slop of 0 can be applied across two SpanTermQuery objects as follows:

SpanQuery q1  = new SpanTermQuery(new Term("studentfirstname", "james"));
 SpanQuery q2  = new SpanTermQuery(new Term("studentsurname", "jones"));
 SpanQuery q2m = new FieldMaskingSpanQuery(q2, "studentfirstname");
 Query q = new SpanNearQuery(new SpanQuery[] { q1, q2m }, -1, false);

to search for 'studentfirstname:james studentsurname:jones' and find teacherid 1 without matching teacherid 2 (which has a 'james' in position 0 and 'jones' in position 1).

Note: as Field returns the masked field, scoring will be done using the Similarity and collection statistics of the field name supplied, but with the term statistics of the real field. This may lead to exceptions, poor performance, and unexpected scoring behavior.

Declaration

public FieldMaskingSpanQuery(SpanQuery maskedQuery, string maskedField)

Parameters

Type	Name	Description
SpanQuery	maskedQuery
string	maskedField

Properties

Field

Returns the name of the field matched by this query.

Note that this may return null if the query matches no terms.

Declaration

public override string Field { get; }

Property Value

Type	Description
string

Overrides

SpanQuery.Field

MaskedQuery

Wrapper to allow SpanQuery objects participate in composite single-field SpanQueries by 'lying' about their search field. That is, the masked SpanQuery will function as normal, but Field simply hands back the value supplied in this class's constructor.

This can be used to support Queries like SpanNearQuery or SpanOrQuery across different fields, which is not ordinarily permitted.

This can be useful for denormalized relational data: for example, when indexing a document with conceptually many 'children':

teacherid: 1
studentfirstname: james
studentsurname: jones
teacherid: 2
studenfirstname: james
studentsurname: smith
studentfirstname: sally
studentsurname: jones

A SpanNearQuery with a slop of 0 can be applied across two SpanTermQuery objects as follows:

SpanQuery q1  = new SpanTermQuery(new Term("studentfirstname", "james"));
 SpanQuery q2  = new SpanTermQuery(new Term("studentsurname", "jones"));
 SpanQuery q2m = new FieldMaskingSpanQuery(q2, "studentfirstname");
 Query q = new SpanNearQuery(new SpanQuery[] { q1, q2m }, -1, false);

to search for 'studentfirstname:james studentsurname:jones' and find teacherid 1 without matching teacherid 2 (which has a 'james' in position 0 and 'jones' in position 1).

Note: as Field returns the masked field, scoring will be done using the Similarity and collection statistics of the field name supplied, but with the term statistics of the real field. This may lead to exceptions, poor performance, and unexpected scoring behavior.

Declaration

public virtual SpanQuery MaskedQuery { get; }

Property Value

Type	Description
SpanQuery

Methods

CreateWeight(IndexSearcher)

Expert: Constructs an appropriate Weight implementation for this query.

Only implemented by primitive queries, which re-write to themselves.

Declaration

public override Weight CreateWeight(IndexSearcher searcher)

Parameters

Type	Name	Description
IndexSearcher	searcher

Returns

Type	Description
Weight

Overrides

SpanQuery.CreateWeight(IndexSearcher)

Equals(object)

Determines whether the specified object is equal to the current object.

Declaration

public override bool Equals(object o)

Parameters

Type	Name	Description
object	o

Returns

Type	Description
bool	true if the specified object is equal to the current object; otherwise, false.

Overrides

Query.Equals(object)

ExtractTerms(ISet<Term>)

Expert: adds all terms occurring in this query to the terms set. Only works if this query is in its rewritten (Rewrite(IndexReader)) form.

Declaration

public override void ExtractTerms(ISet<Term> terms)

Parameters

Type	Name	Description
ISet<Term>	terms

Overrides

Query.ExtractTerms(ISet<Term>)

Exceptions

Type	Condition
InvalidOperationException	If this query is not yet rewritten

GetHashCode()

Serves as the default hash function.

Declaration

public override int GetHashCode()

Returns

Type	Description
int	A hash code for the current object.

Overrides

Query.GetHashCode()

GetSpans(AtomicReaderContext, IBits, IDictionary<Term, TermContext>)

Expert: Returns the matches for this query in an index. Used internally to search for spans.

Declaration

public override Spans GetSpans(AtomicReaderContext context, IBits acceptDocs, IDictionary<Term, TermContext> termContexts)

Parameters

Type	Name	Description
AtomicReaderContext	context
IBits	acceptDocs
IDictionary<Term, TermContext>	termContexts

Returns

Type	Description
Spans

Overrides

SpanQuery.GetSpans(AtomicReaderContext, IBits, IDictionary<Term, TermContext>)

Rewrite(IndexReader)

Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

Declaration

public override Query Rewrite(IndexReader reader)

Parameters

Type	Name	Description
IndexReader	reader

Returns

Type	Description
Query

Overrides

Query.Rewrite(IndexReader)

ToString(string)

Prints a query to a string, with field assumed to be the default field and omitted.

Declaration

public override string ToString(string field)

Parameters

Type	Name	Description
string	field

Returns

Type	Description
string

Overrides

Query.ToString(string)