package org.apache.lucene.search;

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 * reserved.
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 * modification, are permitted provided that the following conditions
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 *       "This product includes software developed by the
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import java.io.IOException;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.Term;

/** The abstract base class for search implementations.
  <p>Subclasses implement search over a single index, over multiple indices,
  and over indices on remote servers.
 */
public abstract class Searcher {

  /** Returns the documents matching <code>query</code>. */
  public final Hits search(Query query) throws IOException {
    return search(query, (Filter)null);
  }

  /** Returns the documents matching <code>query</code> and
    <code>filter</code>. */
  public Hits search(Query query, Filter filter) throws IOException {
    return new Hits(this, query, filter);
  }

  /** Lower-level search API.
   *
   * <p>{@link HitCollector#collect(int,float)} is called for every non-zero
   * scoring document.
   *
   * <p>Applications should only use this if they need <i>all</i> of the
   * matching documents.  The high-level search API ({@link
   * Searcher#search(Query)}) is usually more efficient, as it skips
   * non-high-scoring hits.  */
  public void search(Query query, HitCollector results)
    throws IOException {
    search(query, (Filter)null, results);
  }

  /** Lower-level search API.
   *
   * <p>{@link HitCollector#collect(int,float)} is called for every non-zero
   * scoring document.
   *
   * <p>Applications should only use this if they need <i>all</i> of the
   * matching documents.  The high-level search API ({@link
   * Searcher#search(Query)}) is usually more efficient, as it skips
   * non-high-scoring hits.
   *
   * @param query to match documents
   * @param filter if non-null, a bitset used to eliminate some documents
   * @param results to receive hits
   */
  public abstract void search(Query query, Filter filter, HitCollector results)
    throws IOException;

  /** Frees resources associated with this Searcher. */
  public abstract  void close() throws IOException;

  public abstract int docFreq(Term term) throws IOException;
  public abstract int maxDoc() throws IOException;
  public abstract TopDocs search(Query query, Filter filter, int n)
       throws IOException;

  /** For use by {@link HitCollector} implementations. */
  public abstract Document doc(int i) throws IOException;
}