org.apache.drill.exec.expr.fn.impl

Class StringDistanceFunctions.LongestCommonSubstringDistanceFunction

java.lang.Object

org.apache.drill.exec.expr.fn.impl.StringDistanceFunctions.LongestCommonSubstringDistanceFunction

All Implemented Interfaces:

DrillFunc, DrillSimpleFunc

Enclosing class:

StringDistanceFunctions

public static class StringDistanceFunctions.LongestCommonSubstringDistanceFunction
extends Object
implements DrillSimpleFunc

The Longest common subsequence algorithm returns the length of the longest subsequence that two strings have in common. Two strings that are entirely different, return a value of 0, and two strings that return a value of the commonly shared length implies that the strings are completely the same in value and position. Note: Generally this algorithm is fairly inefficient, as for length m, n of the input CharSequence's left and right respectively, the runtime of the algorithm is O(m*n).

This implementation is based on the Longest Commons Substring algorithm from https://en.wikipedia.org/wiki/Longest_common_subsequence_problem.

Usage: SELECT longest_common_substring_distance( string1, string2 ) FROM...

Constructor Summary

Constructors

Constructor and Description
LongestCommonSubstringDistanceFunction()

Method Summary

Modifier and Type	Method and Description
void	eval()
void	setup()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LongestCommonSubstringDistanceFunction

public LongestCommonSubstringDistanceFunction()

Method Detail

setup

public void setup()

Specified by:

setup in interface DrillSimpleFunc

eval

public void eval()

Specified by:

eval in interface DrillSimpleFunc