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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hive.ql.lib;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.Stack;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.hadoop.hive.ql.parse.SemanticException;
/**
* Rule interface for Nodes Used in Node dispatching to dispatch process/visitor
* functions for Nodes.
*/
public class RuleRegExp implements Rule {
private final String ruleName;
private final Pattern patternWithWildCardChar;
private final String patternWithoutWildCardChar;
private String[] patternORWildChar;
private static final Set wildCards = new HashSet(Arrays.asList(
'[', '^', '$', '*', ']', '+', '|', '(', '\\', '.', '?', ')', '&'));
/**
* The function iterates through the list of wild card characters and sees if
* this regular expression contains a wild card character.
*
* @param pattern
* pattern expressed as a regular Expression
*/
private static boolean patternHasWildCardChar(String pattern) {
if (pattern == null) {
return false;
}
for (char pc : pattern.toCharArray()) {
if (wildCards.contains(pc)) {
return true;
}
}
return false;
}
/**
* The function iterates through the list of wild card characters and sees if
* this regular expression contains only the given char as wild card character.
*
* @param pattern
* pattern expressed as a regular Expression
* @param wcc
* wild card character
*/
private static boolean patternHasOnlyWildCardChar(String pattern, char wcc) {
if (pattern == null) {
return false;
}
boolean ret = true;
boolean hasWildCard = false;
for (char pc : pattern.toCharArray()) {
if (wildCards.contains(pc)) {
hasWildCard = true;
ret = ret && (pc == wcc);
}
}
return ret && hasWildCard;
}
/**
* The rule specified by the regular expression. Note that, the regular
* expression is specified in terms of Node name. For eg: TS.*RS -> means
* TableScan Node followed by anything any number of times followed by
* ReduceSink
*
* @param ruleName
* name of the rule
* @param regExp
* regular expression for the rule
**/
public RuleRegExp(String ruleName, String regExp) {
this.ruleName = ruleName;
if (patternHasWildCardChar(regExp)) {
if (patternHasOnlyWildCardChar(regExp, '|')) {
this.patternWithWildCardChar = null;
this.patternWithoutWildCardChar = null;
this.patternORWildChar = regExp.split("\\|");
} else {
this.patternWithWildCardChar = Pattern.compile(regExp);
this.patternWithoutWildCardChar = null;
this.patternORWildChar = null;
}
} else {
this.patternWithWildCardChar = null;
this.patternWithoutWildCardChar = regExp;
this.patternORWildChar = null;
}
}
/**
* This function returns the cost of the rule for the specified stack when the pattern
* matched for has no wildcard character in it. The function expects patternWithoutWildCardChar
* to be not null.
* @param stack
* Node stack encountered so far
* @return cost of the function
* @throws SemanticException
*/
private int costPatternWithoutWildCardChar(Stack stack) throws SemanticException {
int numElems = (stack != null ? stack.size() : 0);
// No elements
if (numElems == 0) {
return -1;
}
int patLen = patternWithoutWildCardChar.length();
StringBuilder name = new StringBuilder(patLen + numElems);
for (int pos = numElems - 1; pos >= 0; pos--) {
String nodeName = stack.get(pos).getName() + "%";
name.insert(0, nodeName);
if (name.length() >= patLen) {
if (patternWithoutWildCardChar.contentEquals(name)) {
return patLen;
}
break;
}
}
return -1;
}
/**
* This function returns the cost of the rule for the specified stack when the pattern
* matched for has only OR wildcard character in it. The function expects patternORWildChar
* to be not null.
* @param stack
* Node stack encountered so far
* @return cost of the function
* @throws SemanticException
*/
private int costPatternWithORWildCardChar(Stack stack) throws SemanticException {
int numElems = (stack != null ? stack.size() : 0);
// No elements
if (numElems == 0) {
return -1;
}
// These DS are used to cache previously created String
Map cachedNames = new HashMap();
int maxDepth = numElems;
int maxLength = 0;
// For every pattern
for (String pattern : patternORWildChar) {
int patLen = pattern.length();
// If the stack has been explored already till that level,
// obtained cached String
if (cachedNames.containsKey(patLen)) {
if (pattern.contentEquals(cachedNames.get(patLen))) {
return patLen;
}
} else if (maxLength >= patLen) {
// We have already explored the stack deep enough, but
// we do not have a matching
continue;
} else {
// We are going to build the name
StringBuilder name = new StringBuilder(patLen + numElems);
if (maxLength != 0) {
name.append(cachedNames.get(maxLength));
}
for (int pos = maxDepth - 1; pos >= 0; pos--) {
String nodeName = stack.get(pos).getName() + "%";
name.insert(0, nodeName);
// We cache the values
cachedNames.put(name.length(), name.toString());
maxLength = name.length();
maxDepth--;
if (name.length() >= patLen) {
if (pattern.contentEquals(name)) {
return patLen;
}
break;
}
}
}
}
return -1;
}
/**
* This function returns the cost of the rule for the specified stack when the pattern
* matched for has wildcard character in it. The function expects patternWithWildCardChar
* to be not null.
*
* @param stack
* Node stack encountered so far
* @return cost of the function
* @throws SemanticException
*/
private int costPatternWithWildCardChar(Stack stack) throws SemanticException {
int numElems = (stack != null ? stack.size() : 0);
StringBuilder name = new StringBuilder();
Matcher m = patternWithWildCardChar.matcher("");
for (int pos = numElems - 1; pos >= 0; pos--) {
String nodeName = stack.get(pos).getName() + "%";
name.insert(0, nodeName);
m.reset(name);
if (m.matches()) {
return name.length();
}
}
return -1;
}
/**
* Returns true if the rule pattern is valid and has wild character in it.
*/
boolean rulePatternIsValidWithWildCardChar() {
return patternWithoutWildCardChar == null && patternWithWildCardChar != null && this.patternORWildChar == null;
}
/**
* Returns true if the rule pattern is valid and has wild character in it.
*/
boolean rulePatternIsValidWithoutWildCardChar() {
return patternWithWildCardChar == null && patternWithoutWildCardChar != null && this.patternORWildChar == null;
}
/**
* Returns true if the rule pattern is valid and has wild character in it.
*/
boolean rulePatternIsValidWithORWildCardChar() {
return patternWithoutWildCardChar == null && patternWithWildCardChar == null && this.patternORWildChar != null;
}
/**
* This function returns the cost of the rule for the specified stack. Lower
* the cost, the better the rule is matched
*
* @param stack
* Node stack encountered so far
* @return cost of the function
* @throws SemanticException
*/
@Override
public int cost(Stack stack) throws SemanticException {
if (rulePatternIsValidWithoutWildCardChar()) {
return costPatternWithoutWildCardChar(stack);
}
if (rulePatternIsValidWithWildCardChar()) {
return costPatternWithWildCardChar(stack);
}
if (rulePatternIsValidWithORWildCardChar()) {
return costPatternWithORWildCardChar(stack);
}
// If we reached here, either :
// 1. patternWithWildCardChar and patternWithoutWildCardChar are both nulls.
// 2. patternWithWildCardChar and patternWithoutWildCardChar are both not nulls.
// This is an internal error and we should not let this happen, so throw an exception.
throw new SemanticException (
"Rule pattern is invalid for " + getName() + " : patternWithWildCardChar = " +
patternWithWildCardChar + " patternWithoutWildCardChar = " +
patternWithoutWildCardChar);
}
/**
* @return the name of the Node
**/
@Override
public String getName() {
return ruleName;
}
}
