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## 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
`QueryProcessor()`

Method Summary
`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)

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