org.modeshape.graph.query.process
Class ProcessingComponent

java.lang.Object
  org.modeshape.graph.query.process.ProcessingComponent

Direct Known Subclasses:

AbstractAccessComponent, DelegatingComponent, JoinComponent, NoResultsComponent, SetOperationComponent

@NotThreadSafe
public abstract class ProcessingComponent
extends Object

A component that performs (some) portion of the query processing by returning the tuples that result from this stage of processing. Processing components are designed to be assembled into a processing structure, with a single component at the top that returns the results of a query.

Nested Class Summary

protected static interface

ProcessingComponent.DynamicOperation Interface for evaluating a DynamicOperand to return the resulting value.

Constructor Summary

protected

ProcessingComponent(QueryContext context, QueryResults.Columns columns)

Method Summary

void	close() Close these results, allowing any resources to be released.
protected ProcessingComponent.DynamicOperation	createDynamicOperation(TypeSystem typeSystem, Schemata schemata, QueryResults.Columns columns, DynamicOperand operand) Create a ProcessingComponent.DynamicOperation instance that is able to evaluate the supplied DynamicOperand.
protected Comparator<Object[]>	createSortComparator(QueryContext context, QueryResults.Columns columns)
protected List<Object[]>	emptyTuples() Utility method to create a new tuples list that is empty.
abstract List<Object[]>	execute() Execute this stage of processing and return the resulting tuples that each conform to the columns.
QueryResults.Columns	getColumns() Get the column definitions.
QueryContext	getContext() Get the context in which this query is being executed.
protected Problems	problems() Get the container for problems encountered during processing.

Methods inherited from class java.lang.Object

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

Constructor Detail

ProcessingComponent

protected ProcessingComponent(QueryContext context,
                              QueryResults.Columns columns)

Method Detail

getContext

public final QueryContext getContext()

Get the context in which this query is being executed.

Returns:

context

getColumns

public final QueryResults.Columns getColumns()

Get the column definitions.

Returns:

the column mappings; never null

problems

protected final Problems problems()

Get the container for problems encountered during processing.

Returns:

the problems container; never null

execute

public abstract List<Object[]> execute()

Execute this stage of processing and return the resulting tuples that each conform to the columns.

Returns:

the list of tuples, where each tuple corresonds to the columns; never null

close

public void close()

Close these results, allowing any resources to be released.

emptyTuples

protected List<Object[]> emptyTuples()

Utility method to create a new tuples list that is empty.

Returns:

the empty tuples list; never null

createDynamicOperation

protected ProcessingComponent.DynamicOperation createDynamicOperation(TypeSystem typeSystem,
                                                                      Schemata schemata,
                                                                      QueryResults.Columns columns,
                                                                      DynamicOperand operand)

Create a ProcessingComponent.DynamicOperation instance that is able to evaluate the supplied DynamicOperand.

Parameters:

typeSystem - the type system; may not be null

schemata - the schemata; may not be null

columns - the definition of the result columns and the tuples; may not be null

operand - the dynamic operand that is to be evaluated by the returned object; may not be null

Returns:

the dynamic operand operation; never null

createSortComparator

protected Comparator<Object[]> createSortComparator(QueryContext context,
                                                    QueryResults.Columns columns)