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Lucene example source code file (NumericUtils.java)

This example Lucene source code file (NumericUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

illegal, illegalargumentexception, illegalargumentexception, intrangebuilder, invalid, invalid, longrangebuilder, numberformatexception, numberformatexception, numericutils, object, string, string, unsupportedoperationexception

The Lucene NumericUtils.java source code

package org.apache.lucene.util;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * 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
 * 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 org.apache.lucene.analysis.NumericTokenStream; // for javadocs
import org.apache.lucene.document.NumericField; // for javadocs
import org.apache.lucene.search.NumericRangeQuery; // for javadocs
import org.apache.lucene.search.NumericRangeFilter; // for javadocs

/**
 * This is a helper class to generate prefix-encoded representations for numerical values
 * and supplies converters to represent float/double values as sortable integers/longs.
 *
 * <p>To quickly execute range queries in Apache Lucene, a range is divided recursively
 * into multiple intervals for searching: The center of the range is searched only with
 * the lowest possible precision in the trie, while the boundaries are matched
 * more exactly. This reduces the number of terms dramatically.
 *
 * <p>This class generates terms to achieve this: First the numerical integer values need to
 * be converted to strings. For that integer values (32 bit or 64 bit) are made unsigned
 * and the bits are converted to ASCII chars with each 7 bit. The resulting string is
 * sortable like the original integer value. Each value is also prefixed
 * (in the first char) by the <code>shift value (number of bits removed) used
 * during encoding.
 *
 * <p>To also index floating point numbers, this class supplies two methods to convert them
 * to integer values by changing their bit layout: {@link #doubleToSortableLong},
 * {@link #floatToSortableInt}. You will have no precision loss by
 * converting floating point numbers to integers and back (only that the integer form
 * is not usable). Other data types like dates can easily converted to longs or ints (e.g.
 * date to long: {@link java.util.Date#getTime}).
 *
 * <p>For easy usage, the trie algorithm is implemented for indexing inside
 * {@link NumericTokenStream} that can index <code>int, long,
 * <code>float, and double. For querying,
 * {@link NumericRangeQuery} and {@link NumericRangeFilter} implement the query part
 * for the same data types.
 *
 * <p>This class can also be used, to generate lexicographically sortable (according
 * {@link String#compareTo(String)}) representations of numeric data types for other
 * usages (e.g. sorting).
 *
 * @lucene.internal
 *
 * @since 2.9
 */
public final class NumericUtils {

  private NumericUtils() {} // no instance!
  
  /**
   * The default precision step used by {@link NumericField}, {@link NumericTokenStream},
   * {@link NumericRangeQuery}, and {@link NumericRangeFilter} as default
   */
  public static final int PRECISION_STEP_DEFAULT = 4;
  
  /**
   * Expert: Longs are stored at lower precision by shifting off lower bits. The shift count is
   * stored as <code>SHIFT_START_LONG+shift in the first character
   */
  public static final char SHIFT_START_LONG = (char)0x20;

  /**
   * Expert: The maximum term length (used for <code>char[] buffer size)
   * for encoding <code>long values.
   * @see #longToPrefixCoded(long,int,char[])
   */
  public static final int BUF_SIZE_LONG = 63/7 + 2;

  /**
   * Expert: Integers are stored at lower precision by shifting off lower bits. The shift count is
   * stored as <code>SHIFT_START_INT+shift in the first character
   */
  public static final char SHIFT_START_INT  = (char)0x60;

  /**
   * Expert: The maximum term length (used for <code>char[] buffer size)
   * for encoding <code>int values.
   * @see #intToPrefixCoded(int,int,char[])
   */
  public static final int BUF_SIZE_INT = 31/7 + 2;

  /**
   * Expert: Returns prefix coded bits after reducing the precision by <code>shift bits.
   * This is method is used by {@link NumericTokenStream}.
   * @param val the numeric value
   * @param shift how many bits to strip from the right
   * @param buffer that will contain the encoded chars, must be at least of {@link #BUF_SIZE_LONG}
   * length
   * @return number of chars written to buffer
   */
  public static int longToPrefixCoded(final long val, final int shift, final char[] buffer) {
    if (shift>63 || shift<0)
      throw new IllegalArgumentException("Illegal shift value, must be 0..63");
    int nChars = (63-shift)/7 + 1, len = nChars+1;
    buffer[0] = (char)(SHIFT_START_LONG + shift);
    long sortableBits = val ^ 0x8000000000000000L;
    sortableBits >>>= shift;
    while (nChars>=1) {
      // Store 7 bits per character for good efficiency when UTF-8 encoding.
      // The whole number is right-justified so that lucene can prefix-encode
      // the terms more efficiently.
      buffer[nChars--] = (char)(sortableBits & 0x7f);
      sortableBits >>>= 7;
    }
    return len;
  }

  /*
   * Expert: Returns prefix coded bits after reducing the precision by <code>shift bits.
   * This is method is used by {@link LongRangeBuilder}.
   * @param val the numeric value
   * @param shift how many bits to strip from the right
   */
  public static String longToPrefixCoded(final long val, final int shift) {
    final char[] buffer = new char[BUF_SIZE_LONG];
    final int len = longToPrefixCoded(val, shift, buffer);
    return new String(buffer, 0, len);
  }

  /*
   * This is a convenience method, that returns prefix coded bits of a long without
   * reducing the precision. It can be used to store the full precision value as a
   * stored field in index.
   * <p>To decode, use {@link #prefixCodedToLong}.
   */
  public static String longToPrefixCoded(final long val) {
    return longToPrefixCoded(val, 0);
  }
  
  /**
   * Expert: Returns prefix coded bits after reducing the precision by <code>shift bits.
   * This is method is used by {@link NumericTokenStream}.
   * @param val the numeric value
   * @param shift how many bits to strip from the right
   * @param buffer that will contain the encoded chars, must be at least of {@link #BUF_SIZE_INT}
   * length
   * @return number of chars written to buffer
   */
  public static int intToPrefixCoded(final int val, final int shift, final char[] buffer) {
    if (shift>31 || shift<0)
      throw new IllegalArgumentException("Illegal shift value, must be 0..31");
    int nChars = (31-shift)/7 + 1, len = nChars+1;
    buffer[0] = (char)(SHIFT_START_INT + shift);
    int sortableBits = val ^ 0x80000000;
    sortableBits >>>= shift;
    while (nChars>=1) {
      // Store 7 bits per character for good efficiency when UTF-8 encoding.
      // The whole number is right-justified so that lucene can prefix-encode
      // the terms more efficiently.
      buffer[nChars--] = (char)(sortableBits & 0x7f);
      sortableBits >>>= 7;
    }
    return len;
  }

  /*
   * Expert: Returns prefix coded bits after reducing the precision by <code>shift bits.
   * This is method is used by {@link IntRangeBuilder}.
   * @param val the numeric value
   * @param shift how many bits to strip from the right
   */
  public static String intToPrefixCoded(final int val, final int shift) {
    final char[] buffer = new char[BUF_SIZE_INT];
    final int len = intToPrefixCoded(val, shift, buffer);
    return new String(buffer, 0, len);
  }

  /*
   * This is a convenience method, that returns prefix coded bits of an int without
   * reducing the precision. It can be used to store the full precision value as a
   * stored field in index.
   * <p>To decode, use {@link #prefixCodedToInt}.
   */
  public static String intToPrefixCoded(final int val) {
    return intToPrefixCoded(val, 0);
  }

  /*
   * Returns a long from prefixCoded characters.
   * Rightmost bits will be zero for lower precision codes.
   * This method can be used to decode e.g. a stored field.
   * @throws NumberFormatException if the supplied string is
   * not correctly prefix encoded.
   * @see #longToPrefixCoded(long)
   */
  public static long prefixCodedToLong(final String prefixCoded) {
    final int shift = prefixCoded.charAt(0)-SHIFT_START_LONG;
    if (shift>63 || shift<0)
      throw new NumberFormatException("Invalid shift value in prefixCoded string (is encoded value really a LONG?)");
    long sortableBits = 0L;
    for (int i=1, len=prefixCoded.length(); i<len; i++) {
      sortableBits <<= 7;
      final char ch = prefixCoded.charAt(i);
      if (ch>0x7f) {
        throw new NumberFormatException(
          "Invalid prefixCoded numerical value representation (char "+
          Integer.toHexString(ch)+" at position "+i+" is invalid)"
        );
      }
      sortableBits |= ch;
    }
    return (sortableBits << shift) ^ 0x8000000000000000L;
  }

  /*
   * Returns an int from prefixCoded characters.
   * Rightmost bits will be zero for lower precision codes.
   * This method can be used to decode e.g. a stored field.
   * @throws NumberFormatException if the supplied string is
   * not correctly prefix encoded.
   * @see #intToPrefixCoded(int)
   */
  public static int prefixCodedToInt(final String prefixCoded) {
    final int shift = prefixCoded.charAt(0)-SHIFT_START_INT;
    if (shift>31 || shift<0)
      throw new NumberFormatException("Invalid shift value in prefixCoded string (is encoded value really an INT?)");
    int sortableBits = 0;
    for (int i=1, len=prefixCoded.length(); i<len; i++) {
      sortableBits <<= 7;
      final char ch = prefixCoded.charAt(i);
      if (ch>0x7f) {
        throw new NumberFormatException(
          "Invalid prefixCoded numerical value representation (char "+
          Integer.toHexString(ch)+" at position "+i+" is invalid)"
        );
      }
      sortableBits |= ch;
    }
    return (sortableBits << shift) ^ 0x80000000;
  }

  /**
   * Converts a <code>double value to a sortable signed long.
   * The value is converted by getting their IEEE 754 floating-point "double format"
   * bit layout and then some bits are swapped, to be able to compare the result as long.
   * By this the precision is not reduced, but the value can easily used as a long.
   * @see #sortableLongToDouble
   */
  public static long doubleToSortableLong(double val) {
    long f = Double.doubleToRawLongBits(val);
    if (f<0) f ^= 0x7fffffffffffffffL;
    return f;
  }

  /*
   * Convenience method: this just returns:
   *   longToPrefixCoded(doubleToSortableLong(val))
   */
  public static String doubleToPrefixCoded(double val) {
    return longToPrefixCoded(doubleToSortableLong(val));
  }

  /**
   * Converts a sortable <code>long back to a double.
   * @see #doubleToSortableLong
   */
  public static double sortableLongToDouble(long val) {
    if (val<0) val ^= 0x7fffffffffffffffL;
    return Double.longBitsToDouble(val);
  }

  /*
   * Convenience method: this just returns:
   *    sortableLongToDouble(prefixCodedToLong(val))
   */
  public static double prefixCodedToDouble(String val) {
    return sortableLongToDouble(prefixCodedToLong(val));
  }

  /**
   * Converts a <code>float value to a sortable signed int.
   * The value is converted by getting their IEEE 754 floating-point "float format"
   * bit layout and then some bits are swapped, to be able to compare the result as int.
   * By this the precision is not reduced, but the value can easily used as an int.
   * @see #sortableIntToFloat
   */
  public static int floatToSortableInt(float val) {
    int f = Float.floatToRawIntBits(val);
    if (f<0) f ^= 0x7fffffff;
    return f;
  }

  /*
   * Convenience method: this just returns:
   *   intToPrefixCoded(floatToSortableInt(val))
   */
  public static String floatToPrefixCoded(float val) {
    return intToPrefixCoded(floatToSortableInt(val));
  }

  /**
   * Converts a sortable <code>int back to a float.
   * @see #floatToSortableInt
   */
  public static float sortableIntToFloat(int val) {
    if (val<0) val ^= 0x7fffffff;
    return Float.intBitsToFloat(val);
  }

  /*
   * Convenience method: this just returns:
   *    sortableIntToFloat(prefixCodedToInt(val))
   */
  public static float prefixCodedToFloat(String val) {
    return sortableIntToFloat(prefixCodedToInt(val));
  }

  /**
   * Expert: Splits a long range recursively.
   * You may implement a builder that adds clauses to a
   * {@link org.apache.lucene.search.BooleanQuery} for each call to its
   * {@link LongRangeBuilder#addRange(String,String)}
   * method.
   * <p>This method is used by {@link NumericRangeQuery}.
   */
  public static void splitLongRange(final LongRangeBuilder builder,
    final int precisionStep,  final long minBound, final long maxBound
  ) {
    splitRange(builder, 64, precisionStep, minBound, maxBound);
  }
  
  /**
   * Expert: Splits an int range recursively.
   * You may implement a builder that adds clauses to a
   * {@link org.apache.lucene.search.BooleanQuery} for each call to its
   * {@link IntRangeBuilder#addRange(String,String)}
   * method.
   * <p>This method is used by {@link NumericRangeQuery}.
   */
  public static void splitIntRange(final IntRangeBuilder builder,
    final int precisionStep,  final int minBound, final int maxBound
  ) {
    splitRange(builder, 32, precisionStep, minBound, maxBound);
  }
  
  /** This helper does the splitting for both 32 and 64 bit. */
  private static void splitRange(
    final Object builder, final int valSize,
    final int precisionStep, long minBound, long maxBound
  ) {
    if (precisionStep < 1)
      throw new IllegalArgumentException("precisionStep must be >=1");
    if (minBound > maxBound) return;
    for (int shift=0; ; shift += precisionStep) {
      // calculate new bounds for inner precision
      final long diff = 1L << (shift+precisionStep),
        mask = ((1L<nextMaxBound || lowerWrapped || upperWrapped) {
        // We are in the lowest precision or the next precision is not available.
        addRange(builder, valSize, minBound, maxBound, shift);
        // exit the split recursion loop
        break;
      }
      
      if (hasLower)
        addRange(builder, valSize, minBound, minBound | mask, shift);
      if (hasUpper)
        addRange(builder, valSize, maxBound & ~mask, maxBound, shift);
      
      // recurse to next precision
      minBound = nextMinBound;
      maxBound = nextMaxBound;
    }
  }
  
  /** Helper that delegates to correct range builder */
  private static void addRange(
    final Object builder, final int valSize,
    long minBound, long maxBound,
    final int shift
  ) {
    // for the max bound set all lower bits (that were shifted away):
    // this is important for testing or other usages of the splitted range
    // (e.g. to reconstruct the full range). The prefixEncoding will remove
    // the bits anyway, so they do not hurt!
    maxBound |= (1L << shift) - 1L;
    // delegate to correct range builder
    switch(valSize) {
      case 64:
        ((LongRangeBuilder)builder).addRange(minBound, maxBound, shift);
        break;
      case 32:
        ((IntRangeBuilder)builder).addRange((int)minBound, (int)maxBound, shift);
        break;
      default:
        // Should not happen!
        throw new IllegalArgumentException("valSize must be 32 or 64.");
    }
  }

  /**
   * Expert: Callback for {@link #splitLongRange}.
   * You need to overwrite only one of the methods.
   * <p>NOTE: This is a very low-level interface,
   * the method signatures may change in later versions.</font>
   */
  public static abstract class LongRangeBuilder {
    
    /**
     * Overwrite this method, if you like to receive the already prefix encoded range bounds.
     * You can directly build classical (inclusive) range queries from them.
     */
    public void addRange(String minPrefixCoded, String maxPrefixCoded) {
      throw new UnsupportedOperationException();
    }
    
    /**
     * Overwrite this method, if you like to receive the raw long range bounds.
     * You can use this for e.g. debugging purposes (print out range bounds).
     */
    public void addRange(final long min, final long max, final int shift) {
      addRange(longToPrefixCoded(min, shift), longToPrefixCoded(max, shift));
    }
  
  }
  
  /**
   * Expert: Callback for {@link #splitIntRange}.
   * You need to overwrite only one of the methods.
   * <p>NOTE: This is a very low-level interface,
   * the method signatures may change in later versions.</font>
   */
  public static abstract class IntRangeBuilder {
    
    /**
     * Overwrite this method, if you like to receive the already prefix encoded range bounds.
     * You can directly build classical range (inclusive) queries from them.
     */
    public void addRange(String minPrefixCoded, String maxPrefixCoded) {
      throw new UnsupportedOperationException();
    }
    
    /**
     * Overwrite this method, if you like to receive the raw int range bounds.
     * You can use this for e.g. debugging purposes (print out range bounds).
     */
    public void addRange(final int min, final int max, final int shift) {
      addRange(intToPrefixCoded(min, shift), intToPrefixCoded(max, shift));
    }
  
  }
  
}

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