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 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
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 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
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package org.apache.lucene.search;

import java.io.IOException;

A supplier of Scorer. This allows to get an estimate of the cost before building the Scorer. /**
 * A supplier of {@link Scorer}. This allows to get an estimate of the cost before
 * building the {@link Scorer}.
 */
public abstract class ScorerSupplier {

  
Get the Scorer. This may not return null and must be called at most once. 
Params:
leadCost – Cost of the scorer that will be used in order to lead iteration. This can be interpreted as an upper bound of the number of times that DocIdSetIterator.nextDoc, DocIdSetIterator.advance and TwoPhaseIterator.matches will be called. Under doubt, pass Long.MAX_VALUE, which will produce a Scorer that has good iteration capabilities./**
   * Get the {@link Scorer}. This may not return {@code null} and must be called
   * at most once.
   * @param leadCost Cost of the scorer that will be used in order to lead
   * iteration. This can be interpreted as an upper bound of the number of times
   * that {@link DocIdSetIterator#nextDoc}, {@link DocIdSetIterator#advance}
   * and {@link TwoPhaseIterator#matches} will be called. Under doubt, pass
   * {@link Long#MAX_VALUE}, which will produce a {@link Scorer} that has good
   * iteration capabilities.
   */
  public abstract Scorer get(long leadCost) throws IOException;

  
Get an estimate of the Scorer that would be returned by get. This may be a costly operation, so it should only be called if necessary. 
See Also:
DocIdSetIterator.cost/**
   * Get an estimate of the {@link Scorer} that would be returned by {@link #get}.
   * This may be a costly operation, so it should only be called if necessary.
   * @see DocIdSetIterator#cost
   */
  public abstract long cost();

}