org.apache.calcite.rel.rules

Class JoinToMultiJoinRule

java.lang.Object

org.apache.calcite.plan.RelOptRule

org.apache.calcite.rel.rules.JoinToMultiJoinRule

public class JoinToMultiJoinRule
extends RelOptRule

Planner rule to flatten a tree of LogicalJoins into a single MultiJoin with N inputs.

An input is not flattened if the input is a null generating input in an outer join, i.e., either input in a full outer join, the right hand side of a left outer join, or the left hand side of a right outer join.

Join conditions are also pulled up from the inputs into the topmost MultiJoin, unless the input corresponds to a null generating input in an outer join,

Outer join information is also stored in the MultiJoin. A boolean flag indicates if the join is a full outer join, and in the case of left and right outer joins, the join type and outer join conditions are stored in arrays in the MultiJoin. This outer join information is associated with the null generating input in the outer join. So, in the case of a a left outer join between A and B, the information is associated with B, not A.

Here are examples of the MultiJoins constructed after this rule has been applied on following join trees.

• A JOIN B → MJ(A, B)
• A JOIN B JOIN C → MJ(A, B, C)
• A LEFT JOIN B → MJ(A, B), left outer join on input#1
• A RIGHT JOIN B → MJ(A, B), right outer join on input#0
• A FULL JOIN B → MJ[full](A, B)
• A LEFT JOIN (B JOIN C) → MJ(A, MJ(B, C))), left outer join on input#1 in the outermost MultiJoin
• (A JOIN B) LEFT JOIN C → MJ(A, B, C), left outer join on input#2
• (A LEFT JOIN B) JOIN C → MJ(MJ(A, B), C), left outer join on input#1 of the inner MultiJoin TODO
• A LEFT JOIN (B FULL JOIN C) → MJ(A, MJ[full](B, C)), left outer join on input#1 in the outermost MultiJoin
• (A LEFT JOIN B) FULL JOIN (C RIGHT JOIN D) → MJ[full](MJ(A, B), MJ(C, D)), left outer join on input #1 in the first inner MultiJoin and right outer join on input#0 in the second inner MultiJoin

The constructor is parameterized to allow any sub-class of Join, not just LogicalJoin.

See Also:

FilterMultiJoinMergeRule, ProjectMultiJoinMergeRule

Field Summary

Fields

Modifier and Type	Field and Description
static JoinToMultiJoinRule	INSTANCE

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

description, operands

Constructor Summary

Constructors

Constructor and Description
JoinToMultiJoinRule(Class<? extends Join> clazz) Creates a JoinToMultiJoinRule.

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

INSTANCE

public static final JoinToMultiJoinRule INSTANCE

Constructor Detail

JoinToMultiJoinRule

public JoinToMultiJoinRule(Class<? extends Join> clazz)

Creates a JoinToMultiJoinRule.

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)