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## org.modeshape.graph.query.process
Class JoinComponent

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

Direct Known Subclasses:
  MergeJoinComponent, NestedLoopJoinComponent

    public abstract class JoinComponent

extends ProcessingComponent

Nested Class Summary
`protected static interface` | `JoinComponent.Joinable` Interface defining the value of a tuple that is used in the join condition.
`protected static interface` | `JoinComponent.TupleMerger` A component that will merge the supplied tuple on the left side of a join with the supplied tuple on the right side of the join, to produce a single tuple with all components from the left and right tuples.
`protected static interface` | `JoinComponent.ValueSelector` Interface defining the value of a tuple that is used in the join condition.

Nested classes/interfaces inherited from class org.modeshape.graph.query.process.ProcessingComponent
`ProcessingComponent.DynamicOperation`

Field Summary
`protected static Comparator<Location>` | `LOCATION_COMPARATOR`

Constructor Summary
`protected` | `JoinComponent(QueryContext context, ProcessingComponent left, ProcessingComponent right, JoinCondition condition, JoinType joinType)`

Method Summary
`protected static Comparator<Object>` | `comparatorFor(QueryContext context, ProcessingComponent left, ProcessingComponent right, JoinCondition condition)` Create a `Comparable` that can be used to compare the values required to evaluate the supplied join condition.
`protected static JoinComponent.TupleMerger` | `createMerger(QueryResults.Columns joinColumns, QueryResults.Columns leftColumns, QueryResults.Columns rightColumns)` Create a `JoinComponent.TupleMerger` implementation that will combine a tuple fitting the left columns with a tuple fitting the right columns.
`JoinCondition` | `getJoinCondition()` Get the join condition.
`JoinType` | `getJoinType()` Get the type of join this processor represents.
`protected static JoinComponent.Joinable` | `joinableFor(ProcessingComponent left, ProcessingComponent right, JoinCondition condition)` Create a `JoinComponent.ValueSelector` that obtains the value required to use the supplied join condition.
`protected ProcessingComponent` | `left()` Get the processing component that serves as the left side of the join.
`protected QueryResults.Columns` | `leftColunns()` Get the columns definition for the results from the left side of the join.
`protected ProcessingComponent` | `right()` Get the processing component that serves as the right side of the join.
`protected QueryResults.Columns` | `rightColumns()` Get the columns definition for the results from the right side of the join.
`protected static JoinComponent.ValueSelector` | `valueSelectorFor(ProcessingComponent source, JoinCondition condition)` Create a `JoinComponent.ValueSelector` that obtains the value required to use the supplied join condition.

Methods inherited from class org.modeshape.graph.query.process.ProcessingComponent
`close, createDynamicOperation, createSortComparator, emptyTuples, execute, getColumns, getContext, problems`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### LOCATION_COMPARATOR

    protected static final Comparator<Location> LOCATION_COMPARATOR

Constructor Detail

### JoinComponent

    protected JoinComponent(QueryContext context,
                            ProcessingComponent left,
                            ProcessingComponent right,
                            JoinCondition condition,
                            JoinType joinType)

Method Detail

### getJoinType

    public final JoinType getJoinType()

  Get the type of join this processor represents.

  Returns:
    the join type; never null

### getJoinCondition

    public final JoinCondition getJoinCondition()

  Get the join condition.

  Returns:
    the join condition; never null

### left

    protected final ProcessingComponent left()

  Get the processing component that serves as the left side of the join.

  Returns:
    the left-side processing component; never null

### right

    protected final ProcessingComponent right()

  Get the processing component that serves as the right side of the join.

  Returns:
    the right-side processing component; never null

### leftColunns

    protected final QueryResults.Columns leftColunns()

  Get the columns definition for the results from the left side of the join.

  Returns:
    the left-side columns that feed this join; never null

### rightColumns

    protected final QueryResults.Columns rightColumns()

  Get the columns definition for the results from the right side of the join.

  Returns:
    the right-side columns that feed this join; never null

### createMerger

    protected static JoinComponent.TupleMerger createMerger(QueryResults.Columns joinColumns,
                                                            QueryResults.Columns leftColumns,
                                                            QueryResults.Columns rightColumns)

  Create a `JoinComponent.TupleMerger` implementation that will combine a tuple fitting the left columns with a tuple fitting the right columns. This merger will properly place all of the values, locations, and scores such that the tuples always have this arrangement:

          [ v1, v2, ..., vM, loc1, loc2, ..., locN, s1, s2, ..., sN ]

  where M is the number of values in the tuple, and N is the number of sources in the tuple.

  Note that this merger does not actually reduce or combine values. That is done with a particular `JoinComponent` subclass.

  Parameters:
    `joinColumns` - the Columns specification for the joined/merged tuples; may not be null
    `leftColumns` - the Columns specification for the tuple on the left side of the join; may not be null
    `rightColumns` - the Columns specification for the tuple on the right side of the join; may not be null
  Returns:
    the merger implementation that will combine tuples from the left and right to form the merged tuples; never null

### valueSelectorFor

    protected static JoinComponent.ValueSelector valueSelectorFor(ProcessingComponent source,
                                                                  JoinCondition condition)

  Create a `JoinComponent.ValueSelector` that obtains the value required to use the supplied join condition.

  Parameters:
    `source` - the source component; may not be null
    `condition` - the join condition; may not be null
  Returns:
    the value selector; never null

### joinableFor

    protected static JoinComponent.Joinable joinableFor(ProcessingComponent left,
                                                        ProcessingComponent right,
                                                        JoinCondition condition)

  Create a `JoinComponent.ValueSelector` that obtains the value required to use the supplied join condition.

  Parameters:
    `left` - the left source component; may not be null
    `right` - the left source component; may not be null
    `condition` - the join condition; may not be null
  Returns:
    the value selector; never null

### comparatorFor

    protected static Comparator<Object> comparatorFor(QueryContext context,
                                                      ProcessingComponent left,
                                                      ProcessingComponent right,
                                                      JoinCondition condition)

  Create a `Comparable` that can be used to compare the values required to evaluate the supplied join condition.

  Parameters:
    `context` - the context in which this query is being evaluated; may not be null
    `left` - the left source component; may not be null
    `right` - the left source component; may not be null
    `condition` - the join condition; may not be null
  Returns:
    the comparator; never null

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