org.apache.tajo.plan.rewrite

Interface LogicalPlanRewriteRule

All Known Implementing Classes:

FilterPushDownRule, LogicalPlanEqualityTester, PartitionedTableRewriter, ProjectionPushDownRule

public interface LogicalPlanRewriteRule

An interface for a rewrite rule.

Method Summary

Methods

Modifier and Type	Method and Description
String	getName() It returns the rewrite rule name.
boolean	isEligible(OverridableConf queryContext, LogicalPlan plan) This method checks if this rewrite rule can be applied to a given query plan.
LogicalPlan	rewrite(OverridableConf queryContext, LogicalPlan plan) Updates a logical plan and returns an updated logical plan rewritten by this rule.

Method Detail

getName

String getName()

It returns the rewrite rule name. It will be used for debugging and building a optimization history.

Returns:

The rewrite rule name

isEligible

boolean isEligible(OverridableConf queryContext,
                 LogicalPlan plan)

This method checks if this rewrite rule can be applied to a given query plan. For example, the selection push down can not be applied to the query plan without any filter. In such case, it will return false.

Parameters:

plan - The plan to be checked

Returns:

True if this rule can be applied to a given plan. Otherwise, false.

rewrite

LogicalPlan rewrite(OverridableConf queryContext,
                  LogicalPlan plan)
                    throws PlanningException

Updates a logical plan and returns an updated logical plan rewritten by this rule. It must be guaranteed that the input logical plan is not modified even after rewrite. In other words, the rewrite has to modify an plan copied from the input plan.

Parameters:

plan - Input logical plan. It will not be modified.

Returns:

The rewritten logical plan.

Throws:

PlanningException