org.apache.hadoop.hive.ql.lib

Class RuleExactMatch

java.lang.Object

org.apache.hadoop.hive.ql.lib.RuleExactMatch

All Implemented Interfaces:

Rule, SemanticRule

public class RuleExactMatch
extends Object
implements SemanticRule

Implentation of the Rule interface for Nodes Used in Node dispatching to dispatch process/visitor functions for Nodes. The cost method returns 1 if there is an exact match between the expression and the stack, otherwise -1.

Constructor Summary

Constructors

Constructor and Description
RuleExactMatch(String ruleName, String[] pattern) The rule specified as operator names separated by % symbols, the left side represents the bottom of the stack.

Method Summary

Modifier and Type	Method and Description
int	cost(Stack<Node> stack) This function returns the cost of the rule for the specified stack.
String	getName()

Methods inherited from class java.lang.Object

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

Constructor Detail

RuleExactMatch

public RuleExactMatch(String ruleName,
                      String[] pattern)

The rule specified as operator names separated by % symbols, the left side represents the bottom of the stack. E.g. TS%FIL%RS -> means TableScan Node followed by Filter followed by ReduceSink in the tree, or, in terms of the stack, ReduceSink on top followed by Filter followed by TableScan

Parameters:

ruleName - name of the rule

pattern - string specification of the rule

Method Detail

cost

public int cost(Stack<Node> stack)
         throws SemanticException

This function returns the cost of the rule for the specified stack. Returns 1 if there is an exact match with the entire stack, otherwise -1 If any proper substack of the stack matches it will return -1. It only returns 1 if the entire stack matches the rule exactly.

Specified by:

cost in interface Rule

Specified by:

cost in interface SemanticRule

Parameters:

stack - Node stack encountered so far

Returns:

cost of the function

Throws:

SemanticException

getName

public String getName()

Specified by:

getName in interface Rule

Specified by:

getName in interface SemanticRule

Returns:

the name of the Node