org.modeshape.jcr.query.process

Class QueryProcessor<ProcessingContextType>

java.lang.Object

org.modeshape.jcr.query.process.QueryProcessor<ProcessingContextType>

Type Parameters:

ProcessingContextType - the processing context object type

All Implemented Interfaces:

Processor

Direct Known Subclasses:

LuceneQueryEngine.LuceneQueryProcessor

public abstract class QueryProcessor<ProcessingContextType>
extends Object
implements Processor

An abstract Processor implementation that builds a tree of ProcessingComponent objects to perform the different parts of the query processing logic. Subclasses are required to only implement one method: the #createAccessComponent(QueryCommand, QueryContext, PlanNode, Columns, Object) should create a ProcessorComponent object that will perform the (low-level access) query described by the plan given as a parameter.

Constructor Summary

Constructors

Constructor and Description
QueryProcessor()

Method Summary

Methods

Modifier and Type	Method and Description
protected void	closeProcessingContext(ProcessingContextType processingContext) A method that can be overridden to close the supplied processing context.
protected abstract ProcessingComponent	createAccessComponent(QueryCommand originalQuery, QueryContext context, PlanNode accessNode, QueryResults.Columns resultColumns, ProcessingContextType processingContext) Create the ProcessingComponent that processes a single PlanNode.Type.ACCESS branch of a query plan.
protected QueryResults.Columns	createColumnsFor(PlanNode node, QueryResults.Columns projectedColumns)
protected ProcessingComponent	createComponent(QueryCommand originalQuery, QueryContext context, PlanNode node, QueryResults.Columns columns, ProcessingContextType processingContext) Method that is called to build up the ProcessingComponent objects that correspond to the optimized query plan.
protected ProcessingContextType	createProcessingContext(QueryContext queryContext) A method that can be overridden by subclasses to create a single context object used for all the access queries for a single query.
QueryResults	execute(QueryContext context, QueryCommand command, QueryResults.Statistics statistics, PlanNode plan) Process the supplied query plan for the given command and return the results.
protected abstract boolean	supportsPushDownExistConstraints()

Methods inherited from class java.lang.Object

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

Constructor Detail

QueryProcessor

public QueryProcessor()

Method Detail

execute

public QueryResults execute(QueryContext context,
                   QueryCommand command,
                   QueryResults.Statistics statistics,
                   PlanNode plan)

Description copied from interface: Processor

Process the supplied query plan for the given command and return the results.

Specified by:

execute in interface Processor

Parameters:

context - the context in which the command is being processed

command - the command being executed

statistics - the time metrics up until this execution

plan - the plan to be processed

Returns:

the results of the query

createProcessingContext

protected ProcessingContextType createProcessingContext(QueryContext queryContext)

A method that can be overridden by subclasses to create a single context object used for all the access queries for a single query.

Parameters:

queryContext - the context in which the query is being executed; never null

Returns:

the processing context object; may be null

closeProcessingContext

protected void closeProcessingContext(ProcessingContextType processingContext)

A method that can be overridden to close the supplied processing context. This method will always be called after a call to createProcessingContext(QueryContext)

Parameters:

processingContext - the processing context in which the query is being executed; null if createProcessingContext(QueryContext) returned null

supportsPushDownExistConstraints

protected abstract boolean supportsPushDownExistConstraints()

createAccessComponent

protected abstract ProcessingComponent createAccessComponent(QueryCommand originalQuery,
                                        QueryContext context,
                                        PlanNode accessNode,
                                        QueryResults.Columns resultColumns,
                                        ProcessingContextType processingContext)

Create the ProcessingComponent that processes a single PlanNode.Type.ACCESS branch of a query plan.

Parameters:

originalQuery - the original query that is being executed; never null

context - the context in which query is being evaluated; never null

accessNode - the node in the query plan that represents the PlanNode.Type.ACCESS plan; never null

resultColumns - the columns that are to be returned; never null

processingContext - the processing context in which the query is being executed; null if createProcessingContext(QueryContext) returned null

Returns:

the processing component; may not be null

createComponent

protected ProcessingComponent createComponent(QueryCommand originalQuery,
                                  QueryContext context,
                                  PlanNode node,
                                  QueryResults.Columns columns,
                                  ProcessingContextType processingContext)

Method that is called to build up the ProcessingComponent objects that correspond to the optimized query plan. This method is called by #execute(QueryContext, QueryCommand, Statistics, PlanNode) for each of the various PlanNode objects in the optimized query plan, and the method is actually recursive (since the optimized query plan forms a tree). However, whenever this call structure reaches the ACCESS nodes in the query plan (which each represents a separate atomic low-level query to the underlying system), the #createAccessComponent(QueryCommand, QueryContext, PlanNode, Columns, Object) method is called. Subclasses should create an appropriate ProcessingComponent implementation that performs this atomic low-level query.

Parameters:

originalQuery - the original query that is being executed; never null

context - the context in which query is being evaluated

node - the plan node for which the ProcessingComponent is to be created

columns - the definition of the result columns for this portion of the query

processingContext - the processing context in which the query is being executed; null if createProcessingContext(QueryContext) returned null

Returns:

the processing component for this plan node; or null if there was an error recorded in the problems

createColumnsFor

protected QueryResults.Columns createColumnsFor(PlanNode node,
                                    QueryResults.Columns projectedColumns)