com.bigdata.rdf.sparql.ast.hints

Interface IQueryHint<T>

Type Parameters:

T - The generic type of the value space for the query hint.

All Known Implementing Classes:

AbstractBooleanQueryHint, AbstractChunkSizeHint, AbstractQueryHint, AbstractStringQueryHint, BasicBooleanQueryHint, BasicDoubleQueryHint, BasicIntQueryHint, BasicLongQueryHint, BasicStringQueryHint, OptimizerQueryHint

public interface IQueryHint<T>

Interface for declaring query hints.

Version:

$Id$

Author:

Bryan Thompson

Method Summary

Methods

Modifier and Type	Method and Description
T	getDefault() The default value for this query hint (many query hints provide overrides of defaults).
String	getName() The name of the query hint.
void	handle(AST2BOpContext ctx, QueryRoot queryRoot, QueryHintScope scope, ASTBase op, T value) Handle the query hint.
T	validate(String value) Validate the value, returning an object of the appropriate type.

Method Detail

getName

String getName()

The name of the query hint.

getDefault

T getDefault()

The default value for this query hint (many query hints provide overrides of defaults).

validate

T validate(String value)

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

Parameters:

value - The value.

Returns:

The validated value.

Throws:

RuntimeException - if the value can not be validated.

handle

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

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