com.bigdata.rdf.sparql.ast.hints

Class OptimizerQueryHint

java.lang.Object

com.bigdata.rdf.sparql.ast.hints.AbstractQueryHint<QueryOptimizerEnum>

com.bigdata.rdf.sparql.ast.hints.OptimizerQueryHint

All Implemented Interfaces:

IQueryHint<QueryOptimizerEnum>

public final class OptimizerQueryHint
extends AbstractQueryHint<QueryOptimizerEnum>

The query hint governing the choice of the join order optimizer.

Constructor Summary

Constructors

Constructor and Description
OptimizerQueryHint()

Method Summary

Methods

Modifier and Type	Method and Description
void	handle(AST2BOpContext ctx, QueryRoot queryRoot, QueryHintScope scope, ASTBase op, QueryOptimizerEnum value) Handle the query hint.
QueryOptimizerEnum	validate(String value) Validate the value, returning an object of the appropriate type.

Methods inherited from class com.bigdata.rdf.sparql.ast.hints.AbstractQueryHint

_setAnnotation, _setQueryHint, getDefault, getName

Methods inherited from class java.lang.Object

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

Constructor Detail

OptimizerQueryHint

public OptimizerQueryHint()

Method Detail

validate

public QueryOptimizerEnum validate(String value)

Description copied from interface: IQueryHint

Validate the value, returning an object of the appropriate type.

Parameters:

value - The value.

Returns:

The validated value.

handle

public void handle(AST2BOpContext ctx,
          QueryRoot queryRoot,
          QueryHintScope scope,
          ASTBase op,
          QueryOptimizerEnum value)

Description copied from interface: IQueryHint

Handle the query hint.

Note: The name of the query hint is no longer strongly coupled to the name of the annotation. This method may be used to attach zero or more annotations as appropriate to the AST structure. It may also be used to change defaults in the AST2BOpContext or take similar actions.

Note: When scope EQ QueryHintScope.Query, the implementation SHOULD also act on AST2BOpContext.queryHints, setting the value in the global scope.

Parameters:

ctx - The query evaluation context.

queryRoot - The root of the query. This is required to resolve the parent of a query hint inside of a FILTER.

scope - The QueryHintScope specified for the query hint.

op - An AST node to which the hint should bind.

value - The value specified for the query hint.

See Also:

bad performance for FILTER EXISTS , Query hint not recognized in FILTER