Package org.apache.flink.api.common.typeutils.base

Class BasicTypeComparator<T extends Comparable<T>>

    • Field Detail

      • ascendingComparison

        protected final boolean ascendingComparison

    • Constructor Detail

      • BasicTypeComparator

        protected BasicTypeComparator​(boolean ascending)

    • Method Detail

      • hash

        public int hash​(T value)
        Description copied from class: TypeComparator
        Computes a hash value for the given record. The hash value should include all fields in the record relevant to the comparison.

        The hash code is typically not used as it is in hash tables and for partitioning, but it is further scrambled to make sure that a projection of the hash values to a lower cardinality space is as results in a rather uniform value distribution. However, any collisions produced by this method cannot be undone. While it is NOT important to create hash codes that cover the full spectrum of bits in the integer, it IS important to avoid collisions when combining two value as much as possible.

        Specified by:
        hash in class TypeComparator<T extends Comparable<T>>
        Parameters:
        value - The record to be hashed.
        Returns:
        A hash value for the record.
        See Also:
        Object.hashCode()

      • setReference

        public void setReference​(T toCompare)
        Description copied from class: TypeComparator
        Sets the given element as the comparison reference for future calls to TypeComparator.equalToReference(Object) and TypeComparator.compareToReference(TypeComparator). This method must set the given element into this comparator instance's state. If the comparison happens on a subset of the fields from the record, this method may extract those fields.

        A typical example for checking the equality of two elements is the following: 

        
 E e1 = ...;
 E e2 = ...;

 TypeComparator<E> acc = ...;

 acc.setReference(e1);
 boolean equal = acc.equalToReference(e2);
        The rational behind this method is that elements are typically compared using certain features that are extracted from them, (such de-serializing as a subset of fields). When setting the reference, this extraction happens. The extraction needs happen only once per element, even though an element is often compared to multiple other elements, such as when finding equal elements in the process of grouping the elements.
        Specified by:
        setReference in class TypeComparator<T extends Comparable<T>>
        Parameters:
        toCompare - The element to set as the comparison reference.

      • equalToReference

        public boolean equalToReference​(T candidate)
        Description copied from class: TypeComparator
        Checks, whether the given element is equal to the element that has been set as the comparison reference in this comparator instance.
        Specified by:
        equalToReference in class TypeComparator<T extends Comparable<T>>
        Parameters:
        candidate - The candidate to check.
        Returns:
        True, if the element is equal to the comparison reference, false otherwise.
        See Also:
        TypeComparator.setReference(Object)

      • compareToReference

        public int compareToReference​(TypeComparator<T> referencedComparator)
        Description copied from class: TypeComparator
        This method compares the element that has been set as reference in this type accessor, to the element set as reference in the given type accessor. Similar to comparing two elements e1 and e2 via a comparator, this method can be used the following way. 
        
 E e1 = ...;
 E e2 = ...;

 TypeComparator<E> acc1 = ...;
 TypeComparator<E> acc2 = ...;

 acc1.setReference(e1);
 acc2.setReference(e2);

 int comp = acc1.compareToReference(acc2);
        The rational behind this method is that elements are typically compared using certain features that are extracted from them, (such de-serializing as a subset of fields). When setting the reference, this extraction happens. The extraction needs happen only once per element, even though an element is typically compared to many other elements when establishing a sorted order. The actual comparison performed by this method may be very cheap, as it happens on the extracted features.
        Specified by:
        compareToReference in class TypeComparator<T extends Comparable<T>>
        Parameters:
        referencedComparator - The type accessors where the element for comparison has been set as reference.
        Returns:
        A value smaller than zero, if the reference value of referencedAccessors is smaller than the reference value of this type accessor; a value greater than zero, if it is larger; zero, if both are equal.
        See Also:
        TypeComparator.setReference(Object)

      • invertNormalizedKey

        public boolean invertNormalizedKey()
        Description copied from class: TypeComparator
        Flag whether normalized key comparisons should be inverted key should be interpreted inverted, i.e. descending.
        Specified by:
        invertNormalizedKey in class TypeComparator<T extends Comparable<T>>
        Returns:
        True, if all normalized key comparisons should invert the sign of the comparison result, false if the normalized key should be used as is.

      • supportsSerializationWithKeyNormalization

        public boolean supportsSerializationWithKeyNormalization()
        Description copied from class: TypeComparator
        Check whether this comparator supports to serialize the record in a format that replaces its keys by a normalized key.
        Specified by:
        supportsSerializationWithKeyNormalization in class TypeComparator<T extends Comparable<T>>
        Returns:
        True, if the comparator supports that specific form of serialization, false if not.

      • extractKeys

        public int extractKeys​(Object record,
                       Object[] target,
                       int index)
        Description copied from class: TypeComparator
        Extracts the key fields from a record. This is for use by the PairComparator to provide interoperability between different record types. Note, that at least one key should be extracted.
        Specified by:
        extractKeys in class TypeComparator<T extends Comparable<T>>
        Parameters:
        record - The record that contains the key(s)
        target - The array to write the key(s) into.
        index - The offset of the target array to start writing into.
        Returns:
        the number of keys added to target.