org.cdlib.xtf.textEngine

Class XtfBigramQueryRewriter

Object

QueryRewriter

BigramQueryRewriter

XtfBigramQueryRewriter

public class XtfBigramQueryRewriter
extends BigramQueryRewriter

Rewrites a query to eliminate stop words by combining them with adjacent non-stop-words, forming "bi-grams". This is a fairly in-depth process, as bi-gramming across NEAR and OR queries is complex.

Nested Class Summary

Nested classes/interfaces inherited from class QueryRewriter

QueryRewriter.SpanClauseJoiner

Field Summary

Fields

Modifier and Type	Field and Description
static Tester	tester Basic regression test
private Set	tokenizedFields

Fields inherited from class BigramQueryRewriter

maxSlop, removedTerms, stopSet

Constructor Summary

Constructors

Constructor and Description
XtfBigramQueryRewriter(Set stopSet, int maxSlop, Set tokFields) Constructs a rewriter using the given stopword set.

Method Summary

Modifier and Type	Method and Description
protected Query	rewrite(MoreLikeThisQuery mlt) Rewrite a "more like this" query
protected Query	rewrite(NumericRangeQuery nrq) Rewrite a numeric range query
protected Query	rewrite(SpanExactQuery q) Rewrite a span EXACT query.
protected Query	rewrite(SpanSectionTypeQuery stq) Rewrite a section type query.
Query	rewriteQuery(Query q) Rewrite a query of any supported type.

Methods inherited from class BigramQueryRewriter

bigramQueries, bigramTermsExact, bigramTermsInexact, convertToSpanQuery, extractTerm, extractTermText, glomInside, glomInside, glomInside, glomQueries, isBigram, makeStopSet, newTerm, reduceBoost, rewrite, rewrite, rewrite, rewrite, rewriteClauses

Methods inherited from class QueryRewriter

combineBoost, copyBoost, copyBoost, forceRewrite, rewrite, rewrite, rewrite, rewrite, rewrite, rewrite, rewrite, rewrite, rewriteClauses

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

tokenizedFields

private Set tokenizedFields

tester

public static final Tester tester

Basic regression test

Constructor Detail

XtfBigramQueryRewriter

public XtfBigramQueryRewriter(Set stopSet,
                              int maxSlop,
                              Set tokFields)

Constructs a rewriter using the given stopword set.

Parameters:

stopSet - Set of stopwords to remove or bi-gram. This can be constructed easily by calling BigramQueryRewriter.makeStopSet(String).

maxSlop - Maximum slop to allow in a query, based on the index being queried.

tokFields - List of fields that are tokenized. We won't rewrite queries for non-tokenized fields.

Method Detail

rewriteQuery

public Query rewriteQuery(Query q)

Rewrite a query of any supported type. Stop words will either be removed or bi-grammed. Skips all queries for un-tokenized fields.

Overrides:

rewriteQuery in class QueryRewriter

Parameters:

q - Query to rewrite

Returns:

A new query, or 'q' unchanged if no change was needed.

rewrite

protected Query rewrite(SpanSectionTypeQuery stq)

Rewrite a section type query. If's very simple: simply rewrite the sub-queries.

Parameters:

stq - The query to rewrite

Returns:

Rewritten version, or 'nq' unchanged if no changed needed.

rewrite

protected Query rewrite(SpanExactQuery q)

Rewrite a span EXACT query. Stop words will be bi-grammed into adjacent terms.

Parameters:

q - The query to rewrite

Returns:

Rewritten version, or 'q' unchanged if no changed needed.

rewrite

protected Query rewrite(MoreLikeThisQuery mlt)

Rewrite a "more like this" query

rewrite

protected Query rewrite(NumericRangeQuery nrq)

Rewrite a numeric range query