org.apache.calcite.rel.rules

Class JoinCommuteRule

java.lang.Object

org.apache.calcite.plan.RelOptRule

org.apache.calcite.rel.rules.JoinCommuteRule

public class JoinCommuteRule
extends RelOptRule

Planner rule that permutes the inputs to a Join.

Permutation of outer joins can be turned on/off by specifying the swapOuter flag in the constructor.

To preserve the order of columns in the output row, the rule adds a Project.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	JoinCommuteRule.VariableReplacer Walks over an expression, replacing references to fields of the left and right inputs.

Field Summary

Fields

Modifier and Type	Field and Description
static JoinCommuteRule	INSTANCE Instance of the rule that only swaps inner joins.
static JoinCommuteRule	SWAP_OUTER Instance of the rule that swaps outer joins as well as inner joins.
private boolean	swapOuter

Fields inherited from class org.apache.calcite.plan.RelOptRule

description, operands, relBuilderFactory

Constructor Summary

Constructors

Modifier	Constructor and Description
private	JoinCommuteRule(boolean swapOuter)
	JoinCommuteRule(Class<? extends Join> clazz, RelBuilderFactory relBuilderFactory, boolean swapOuter) Creates a JoinCommuteRule.
	JoinCommuteRule(Class<? extends Join> clazz, RelFactories.ProjectFactory projectFactory) Deprecated.
	JoinCommuteRule(Class<? extends Join> clazz, RelFactories.ProjectFactory projectFactory, boolean swapOuter) Deprecated.

Method Summary

Modifier and Type	Method and Description
void	onMatch(RelOptRuleCall call) Receives notification about a rule match.
static RelNode	swap(Join join) Returns a relational expression with the inputs switched round.
static RelNode	swap(Join join, boolean swapOuterJoins) Returns a relational expression with the inputs switched round.

Methods inherited from class org.apache.calcite.plan.RelOptRule

any, convert, convert, convertList, convertOperand, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, matches, none, operand, operand, operand, operand, operand, some, toString, unordered

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

INSTANCE

public static final JoinCommuteRule INSTANCE

Instance of the rule that only swaps inner joins.

SWAP_OUTER

public static final JoinCommuteRule SWAP_OUTER

Instance of the rule that swaps outer joins as well as inner joins.

swapOuter

private final boolean swapOuter

Constructor Detail

JoinCommuteRule

public JoinCommuteRule(Class<? extends Join> clazz,
                       RelBuilderFactory relBuilderFactory,
                       boolean swapOuter)

Creates a JoinCommuteRule.

JoinCommuteRule

private JoinCommuteRule(boolean swapOuter)

JoinCommuteRule

@Deprecated
public JoinCommuteRule(Class<? extends Join> clazz,
                                   RelFactories.ProjectFactory projectFactory)

Deprecated.

JoinCommuteRule

@Deprecated
public JoinCommuteRule(Class<? extends Join> clazz,
                                   RelFactories.ProjectFactory projectFactory,
                                   boolean swapOuter)

Deprecated.

Method Detail

swap

public static RelNode swap(Join join)

Returns a relational expression with the inputs switched round. Does not modify join. Returns null if the join cannot be swapped (for example, because it is an outer join).

swap

public static RelNode swap(Join join,
                           boolean swapOuterJoins)

Returns a relational expression with the inputs switched round. Does not modify join. Returns null if the join cannot be swapped (for example, because it is an outer join).

Parameters:

join - join to be swapped

swapOuterJoins - whether outer joins should be swapped

Returns:

swapped join if swapping possible; else null

onMatch

public void onMatch(RelOptRuleCall call)

Description copied from class: RelOptRule

Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.apache.calcite.rel.RelNode, java.util.Map<org.apache.calcite.rel.RelNode, org.apache.calcite.rel.RelNode>) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

call - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)