Package org.apache.calcite.plan

Class SubstitutionVisitor.UnifyRule

java.lang.Object

org.apache.calcite.plan.SubstitutionVisitor.UnifyRule

Direct Known Subclasses:

SubstitutionVisitor.AbstractUnifyRule

Enclosing class:

SubstitutionVisitor

protected abstract static class SubstitutionVisitor.UnifyRule
extends java.lang.Object

Rule that attempts to match a query relational expression against a target relational expression.

The rule declares the query and target types; this allows the engine to fire only a few rules in a given context.

Field Summary

Fields

Modifier and Type	Field	Description
protected SubstitutionVisitor.Operand	queryOperand
protected int	slotCount
protected SubstitutionVisitor.Operand	targetOperand

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	UnifyRule(int slotCount, SubstitutionVisitor.Operand queryOperand, SubstitutionVisitor.Operand targetOperand)

Method Summary

Modifier and Type	Method	Description
protected abstract SubstitutionVisitor.UnifyResult	apply(SubstitutionVisitor.UnifyRuleCall call)	Applies this rule to a particular node in a query.
protected <E> com.google.common.collect.ImmutableList<E>	copy(E[] slots, int slotCount)
protected SubstitutionVisitor.UnifyRuleCall	match(SubstitutionVisitor visitor, MutableRel query, MutableRel target)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

slotCount

protected final int slotCount

queryOperand

protected final SubstitutionVisitor.Operand queryOperand

targetOperand

protected final SubstitutionVisitor.Operand targetOperand

Constructor Detail

UnifyRule

protected UnifyRule(int slotCount,
                    SubstitutionVisitor.Operand queryOperand,
                    SubstitutionVisitor.Operand targetOperand)

Method Detail

apply

protected abstract SubstitutionVisitor.UnifyResult apply(SubstitutionVisitor.UnifyRuleCall call)

Applies this rule to a particular node in a query. The goal is to convert query into target. Before the rule is invoked, Calcite has made sure that query's children are equivalent to target's children.

There are 3 possible outcomes:

• query already exactly matches target; returns target
• query is sufficiently close to a match for target; returns target
• query cannot be made to match target; returns null

REVIEW: Is possible that we match query PLUS one or more of its ancestors?

Parameters:

call - Input parameters

match

protected SubstitutionVisitor.UnifyRuleCall match(SubstitutionVisitor visitor,
                                                  MutableRel query,
                                                  MutableRel target)

copy

protected <E> com.google.common.collect.ImmutableList<E> copy(E[] slots,
                                                              int slotCount)