com.bigdata.rdf.sparql.ast

Enum FilterExistsModeEnum

java.lang.Object

java.lang.Enum<FilterExistsModeEnum>

com.bigdata.rdf.sparql.ast.FilterExistsModeEnum

All Implemented Interfaces:

Serializable, Comparable<FilterExistsModeEnum>

public enum FilterExistsModeEnum
extends Enum<FilterExistsModeEnum>

Used to specify the query plan for FILTER (NOT) EXISTS. There are two basic plans: vectored sub-plan and subquery with LIMIT ONE. Each plan has its advantages.

Author:

Bryan Thompson

See Also:

bad performance for FILTER EXISTS

Enum Constant Summary

Enum Constants

Enum Constant and Description
SubQueryLimitOne This evaluation mode routes each source solution (one by one) into a separate subquery and imposes a LIMIT ONE.
VectoredSubPlan This evaluation mode builds a hash index from all source solutions, vectors the solutions from the hash index into the sub-plan, and the does a hash join of the sub-plan with the hash index to determine which solutions pass the filter.

Method Summary

Methods

Modifier and Type	Method and Description
static FilterExistsModeEnum	valueOf(String name) Returns the enum constant of this type with the specified name.
static FilterExistsModeEnum[]	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

VectoredSubPlan

public static final FilterExistsModeEnum VectoredSubPlan

This evaluation mode builds a hash index from all source solutions, vectors the solutions from the hash index into the sub-plan, and the does a hash join of the sub-plan with the hash index to determine which solutions pass the filter.

This plan solves the FILTER (NOT) EXISTS for multiple source solutions at the same time (vectoring). It is more efficient if the sub-plan requires relatively little work per solution to fully evaluate the sub-plan and there are a large number of solutions flowing into the FILTER (NOT) EXISTS.

SubQueryLimitOne

public static final FilterExistsModeEnum SubQueryLimitOne

This evaluation mode routes each source solution (one by one) into a separate subquery and imposes a LIMIT ONE.

This plan is more efficient if there are many solutions to the FILTER for each source solution, if it is relatively expensive to find all such solutions, and if there are relatively few source solutions. Under these conditions, the FILTER (NOT) EXISTS sub-query is cutoff once it finds the first solution to each source solution and the overhead of submitting multiple sub-queries is modest because there are not that many source solution that need to flow into the FILTER.

Method Detail

values

public static FilterExistsModeEnum[] 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 (FilterExistsModeEnum c : FilterExistsModeEnum.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static FilterExistsModeEnum 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