com.apple.foundationdb.tuple

Class IterableComparator

java.lang.Object

com.apple.foundationdb.tuple.IterableComparator

All Implemented Interfaces:

java.util.Comparator<java.lang.Iterable<?>>

public class IterableComparator
extends java.lang.Object
implements java.util.Comparator<java.lang.Iterable<?>>

A Tuple-compatible Comparator that will sort Iterables in a manner that is consistent with the byte-representation of Tuples. In particular, if one has two Tuples, tuple1 and tuple2, it is the case that:

 
    tuple1.compareTo(tuple2)
      == new IterableComparator().compare(tuple1, tuple2)
      == new IterableComparator().compare(tuple1.getItems(), tuple2.getItems()),
      == ByteArrayUtil.compareUnsigned(tuple1.pack(), tuple2.pack())
 

The individual elements of the Iterable must be of a type that can be serialized by a Tuple. For items of identical types, they will be sorted in a way that is consistent with their natural ordering with a few caveats:

• For floating point types, negative NaN values are sorted before all regular values, and positive NaN values are sorted after all regular values.
• Single-precision floating point numbers are sorted before all double-precision floating point numbers.
• UUIDs are sorted by their unsigned Big-Endian byte representation rather than their signed byte representation (which is the behavior of UUID.compareTo()).
• Strings are sorted explicitly by their UTF-8 byte representation
• Nested Tuples and Lists are sorted element-wise.

Constructor Summary

Constructors

Constructor and Description
IterableComparator() Creates a new IterableComparator.

Method Summary

Modifier and Type	Method and Description
int	compare(java.lang.Iterable<?> iterable1, java.lang.Iterable<?> iterable2) Compare two Iterables in a way consistent with their byte representation.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, equals, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Constructor Detail

IterableComparator

public IterableComparator()

Creates a new IterableComparator. This Comparator has no internal state.

Method Detail

compare

public int compare(java.lang.Iterable<?> iterable1,
                   java.lang.Iterable<?> iterable2)

Compare two Iterables in a way consistent with their byte representation. This is done element-wise and is consistent with a number of other ways of sorting Tuples. This will raise an IllegalArgumentException if any of the items of either Iterable cannot be serialized by a Tuple.

Specified by:

compare in interface java.util.Comparator<java.lang.Iterable<?>>

Parameters:

iterable1 - the first Iterable of items

iterable2 - the second Iterable of items

Returns:

a negative number if the first iterable would sort before the second when serialized, a positive number if the opposite is true, and zero if the two are equal