org.apache.calcite.rel.rules

Class JoinPushThroughJoinRule

java.lang.Object

org.apache.calcite.plan.RelOptRule

org.apache.calcite.rel.rules.JoinPushThroughJoinRule

public class JoinPushThroughJoinRule
extends RelOptRule

Rule that pushes the right input of a join into through the left input of the join, provided that the left input is also a join.

Thus, (A join B) join C becomes (A join C) join B. The advantage of applying this rule is that it may be possible to apply conditions earlier. For instance,

(sales as s join product_class as pc on true)
 join product as p
 on s.product_id = p.product_id
 and p.product_class_id = pc.product_class_id

becomes

(sales as s join product as p on s.product_id = p.product_id)
 join product_class as pc
 on p.product_class_id = pc.product_class_id

Before the rule, one join has two conditions and the other has none (ON TRUE). After the rule, each join has one condition.

Field Summary

Fields

Modifier and Type	Field and Description
static RelOptRule	LEFT Instance of the rule that works on logical joins only, and pushes to the left.
static RelOptRule	RIGHT Instance of the rule that works on logical joins only, and pushes to the right.

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

description, operands

Constructor Summary

Constructors

Constructor and Description
JoinPushThroughJoinRule(String description, boolean right, Class<? extends Join> clazz, RelFactories.ProjectFactory projectFactory) Creates a JoinPushThroughJoinRule.

Method Summary

Methods

Modifier and Type	Method and Description
void	onMatch(RelOptRuleCall call) Receives notification about a rule match.

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

any, convert, convert, convertList, 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

RIGHT

public static final RelOptRule RIGHT

Instance of the rule that works on logical joins only, and pushes to the right.

LEFT

public static final RelOptRule LEFT

Instance of the rule that works on logical joins only, and pushes to the left.

Constructor Detail

JoinPushThroughJoinRule

public JoinPushThroughJoinRule(String description,
                       boolean right,
                       Class<? extends Join> clazz,
                       RelFactories.ProjectFactory projectFactory)

Creates a JoinPushThroughJoinRule.

Method Detail

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)