SpanNotNearQuery.java

package org.apache.lucene.search.spans;


/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import java.io.IOException;
import java.util.Collection;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Explanation;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.Searcher;

/**
 * Removes matches which from one SpanQuery which are too close to
 * spans from another SpanQuery.
 */
public class SpanNotNearQuery extends SpanQuery 
{
  private SpanQuery include;
  private SpanQuery exclude;
  private int slop;

  /** Construct a SpanNotQuery matching spans from <code>include</code> which
   * have no overlap with spans from <code>exclude</code>.*/
  public SpanNotNearQuery(SpanQuery include, SpanQuery exclude, int slop) 
  {
    this.include = include;
    this.exclude = exclude;
    this.slop = slop;

    if (!include.getField().equals(exclude.getField()))
      throw new IllegalArgumentException("Clauses must have same field.");
  }

  /** Return the SpanQuery whose matches are filtered. */
  public SpanQuery getInclude() {
    return include;
  }

  /** Return the SpanQuery whose matches must not overlap those returned. */
  public SpanQuery getExclude() {
    return exclude;
  }

  /** Return the distance that must separate matches from excluded spans.*/
  public int getSlop() {
    return slop;
  }

  public String getField() {
    return include.getField();
  }

  public Collection getTerms() {
    return include.getTerms();
  }

  public Query[] getSubQueries() {
    Query[] result = new Query[2];
    result[0] = include;
    result[1] = exclude;
    return result;
  }

  public Query rewrite(IndexReader reader)
    throws IOException 
  {
    SpanQuery rewrittenInclude = (SpanQuery)include.rewrite(reader);
    SpanQuery rewrittenExclude = (SpanQuery)exclude.rewrite(reader);
    if (rewrittenInclude == include && rewrittenExclude == exclude)
      return this;
    SpanNotNearQuery clone = (SpanNotNearQuery)this.clone();
    clone.include = rewrittenInclude;
    clone.exclude = rewrittenExclude;
    return clone;
  }

  public String toString(String field) {
    StringBuffer buffer = new StringBuffer();
    buffer.append("spanNotNear(");
    buffer.append(include.toString(field));
    buffer.append(", ");
    buffer.append(exclude.toString(field));
    buffer.append(")");
    return buffer.toString();
  }

  public Spans getSpans(final IndexReader reader, final Searcher searcher)
    throws IOException 
  {
    return new Spans() 
    {
      private Spans includeSpans = include.getSpans(reader, searcher);
      private boolean moreInclude = true;
      private Spans excludeSpans = exclude.getSpans(reader, searcher);
      private boolean moreExclude = excludeSpans.next();

      public boolean next()
        throws IOException 
      {
        if (moreInclude) // move to next include
          moreInclude = includeSpans.next();

        return advance();
      }

      private boolean advance()
        throws IOException 
      {
        while (moreInclude && moreExclude) 
        {
          if (includeSpans.doc() > excludeSpans.doc()) // skip exclude
            moreExclude = excludeSpans.skipTo(includeSpans.doc());

          while (moreExclude // while exclude is before
                  &&
                 includeSpans.doc() == excludeSpans.doc() &&
                 excludeSpans.end() <= (includeSpans.start() - slop)) 
          {
            moreExclude = excludeSpans.next(); // increment exclude
          }

          if (!moreExclude // if no intersection
               ||
              includeSpans.doc() != excludeSpans.doc() ||
              excludeSpans.start() >= (includeSpans.end() + slop))
            break; // we found a match

          moreInclude = includeSpans.next(); // intersected: keep scanning
        }
        return moreInclude;
      }

      public boolean skipTo(int target)
        throws IOException 
      {
        if (moreInclude) // skip include
          moreInclude = includeSpans.skipTo(target);

        return advance();
      }

      public int doc() {
        return includeSpans.doc();
      }

      public int start() {
        return includeSpans.start();
      }

      public int end() {
        return includeSpans.end();
      }

      public float score() {
        return includeSpans.score() * getBoost();
      }

      public String toString() {
        return "spans(" + SpanNotNearQuery.this.toString() + ")";
      }

      public Explanation explain()
        throws IOException 
      {
        if (getBoost() == 1.0f)
          return includeSpans.explain();

        Explanation result = new Explanation(0,
                                             "weight(" + toString() +
                                             "), product of:");

        Explanation boostExpl = new Explanation(getBoost(), "boost");
        result.addDetail(boostExpl);

        Explanation inclExpl = includeSpans.explain();
        result.addDetail(inclExpl);

        result.setValue(boostExpl.getValue() * inclExpl.getValue());
        return result;
      }
    };
  }
}