Package org.apache.druid.java.util.common

Enum StringEncoding

  • All Implemented Interfaces:
    Serializable, Comparable<StringEncoding>, Cacheable
    public enum StringEncoding
extends Enum<StringEncoding>
implements Cacheable
    An enum that provides a way for users to specify what encoding should be used when hashing strings. The main reason for this setting's existence is getting the best performance possible. When operating on memory mapped segments -- which store strings as UTF-8 -- it is fastest to use "UTF8". When operating on the result of expressions, or on an in-heap IncrementalIndex -- which use Java strings -- it is fastest to use "UTF16LE". This decision cannot be made locally, because different encodings do not generate equivalent hashes, and therefore they are not mergeable. The decision must be made globally by the end user or by the SQL planner, and should be based on where most input strings are expected to come from. Currently, UTF8 and UTF16LE are the only two options, because there are no situations where other options would be higher-performing.

    • Method Detail

      • values

        public static StringEncoding[] values()
        Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows: 
        for (StringEncoding c : StringEncoding.values())
    System.out.println(c);
        Returns:
        an array containing the constants of this enum type, in the order they are declared

      • valueOf

        public static StringEncoding valueOf​(String name)
        Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
        Parameters:
        name - the name of the enum constant to be returned.
        Returns:
        the enum constant with the specified name
        Throws:
        IllegalArgumentException - if this enum type has no constant with the specified name
        NullPointerException - if the argument is null

      • getCacheKey

        public byte[] getCacheKey()
        Description copied from interface: Cacheable
        Get a byte array used as a cache key.
        Specified by:
        getCacheKey in interface Cacheable
        Returns:
        a cache key