Package com.complexible.stardog

Enum QueryPlanReuse

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Comparable<QueryPlanReuse>
    public enum QueryPlanReuse
extends java.lang.Enum<QueryPlanReuse>
    Options for configuring how Stardog will reuse query plans. Stardog answers queries by first generating an execution plan. Generating an optimal query plan is hard and time-consuming so these plans are cached and reused for structurally equivalent queries; i.e. queries such that one can be transformed into another by replacing constants. This enumeration defines different conditions under which a cached plan will be reused.
    Since:
    4.0.5
    Version:
    4.0.5
    Author:
    Evren Sirin

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description
      ALWAYS
      Always reuse cached query plans for structurally equivalent queries.
      CARDINALITY
      Reuse cached query plans for structurally equivalent queries if the cardinality estimations of scans are similar.
      NEVER
      Never reuse cached query plans.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static QueryPlanReuse valueOf​(java.lang.String name)
      Returns the enum constant of this type with the specified name.
      static QueryPlanReuse[] values()
      Returns an array containing the constants of this enum type, in the order they are declared.

      • Methods inherited from class java.lang.Enum

        clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

    • Enum Constant Detail

      • ALWAYS

        public static final QueryPlanReuse ALWAYS
        Always reuse cached query plans for structurally equivalent queries.

      • NEVER

        public static final QueryPlanReuse NEVER
        Never reuse cached query plans. This strategy degrades query answering performance significantly and should not be used except for debugging purposes.

      • CARDINALITY

        public static final QueryPlanReuse CARDINALITY
        Reuse cached query plans for structurally equivalent queries if the cardinality estimations of scans are similar. This option is useful if the queries to a database involve constants with very different selectivities. If cached plans are always reused then the first query plan that is cached will be reused for all other queries that might not be optimal. Checking cardinality estimations first avoids this problem but introduces some slight overhead for query answering.

    • Method Detail

      • values

        public static QueryPlanReuse[] 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 (QueryPlanReuse c : QueryPlanReuse.values())
    System.out.println(c);
        Returns:
        an array containing the constants of this enum type, in the order they are declared

      • valueOf

        public static QueryPlanReuse valueOf​(java.lang.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:
        java.lang.IllegalArgumentException - if this enum type has no constant with the specified name
        java.lang.NullPointerException - if the argument is null