org.alfresco.repo.search.impl.lucene.analysis
Class NumericEncoder

java.lang.Object
  extended by org.alfresco.repo.search.impl.lucene.analysis.NumericEncoder

public class NumericEncoder
extends java.lang.Object

Support to encode numeric types in the lucene index. To support range queries in the lucene index numeric types need to be indexed specially. This has been addressed for int and long types for lucene and limited support (via scaling) for float and double. The implementation splits an int, long, float or double into the sign bit, optional exponent and mantissa either from the int or long format or its IEEE 754 byte representation. To index content so small negative numbers are indexed correctly and are after big negative numbers in range queries. The algorithm finds the sign, if the number is negative, then the mantissa and exponent are XORed against the appropriate masks. This reverses the order. As negative numbers appear first in the list their sign bit is 0 and positive numbers are 1.


Method Summary
static int decodeInt(java.lang.String hex)
           
static long decodeLong(java.lang.String hex)
          Secode a long
static java.lang.String encode(double doubleToEncode)
          Encode a double into a string that orders correctly according to string comparison.
static java.lang.String encode(float floatToEncode)
          Encode a float into a string that orders correctly according to string comparison.
static java.lang.String encode(int intToEncode)
          Encode an integer into a string that orders correctly using string comparison Integer.MIN_VALUE encodes as 00000000 and MAX_VALUE as ffffffff.
static java.lang.String encode(long longToEncode)
          Encode a long into a string that orders correctly using string comparison Long.MIN_VALUE encodes as 0000000000000000 and MAX_VALUE as ffffffffffffffff.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

encode

public static java.lang.String encode(int intToEncode)
Encode an integer into a string that orders correctly using string comparison Integer.MIN_VALUE encodes as 00000000 and MAX_VALUE as ffffffff.

Parameters:
intToEncode -
Returns:
the encoded string

encode

public static java.lang.String encode(long longToEncode)
Encode a long into a string that orders correctly using string comparison Long.MIN_VALUE encodes as 0000000000000000 and MAX_VALUE as ffffffffffffffff.

Parameters:
longToEncode -
Returns:
- the encoded string

decodeLong

public static long decodeLong(java.lang.String hex)
Secode a long

Parameters:
hex -
Returns:
- the decoded string

decodeInt

public static int decodeInt(java.lang.String hex)

encode

public static java.lang.String encode(float floatToEncode)
Encode a float into a string that orders correctly according to string comparison. Note that there is no negative NaN but there are codings that imply this. So NaN and -Infinity may not compare as expected.

Parameters:
floatToEncode -
Returns:
- the encoded string

encode

public static java.lang.String encode(double doubleToEncode)
Encode a double into a string that orders correctly according to string comparison. Note that there is no negative NaN but there are codings that imply this. So NaN and -Infinity may not compare as expected.

Parameters:
doubleToEncode -
Returns:
the encoded string


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