/*
*
* * Copyright 2014 Orient Technologies LTD (info(at)orientechnologies.com)
* *
* * Licensed 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.
* *
* * For more information: http://www.orientechnologies.com
*
*/
package com.orientechnologies.orient.core.sql;
import com.orientechnologies.common.util.OPair;
import com.orientechnologies.orient.core.index.OIndex;
import com.orientechnologies.orient.core.index.OIndexDefinition;
import java.util.List;
/**
* @author Artem Orobets (enisher-at-gmail.com)
*/
public class OOrderByOptimizer {
boolean canBeUsedByOrderBy(OIndex<?> index, List<OPair<String, String>> orderedFields) {
if (orderedFields.isEmpty())
return false;
if (!index.supportsOrderedIterations())
return false;
final OIndexDefinition definition = index.getDefinition();
final List<String> fields = definition.getFields();
final int endIndex = Math.min(fields.size(), orderedFields.size());
final String firstOrder = orderedFields.get(0).getValue();
for (int i = 0; i < endIndex; i++) {
final OPair<String, String> pair = orderedFields.get(i);
if (!firstOrder.equals(pair.getValue()))
return false;
final String orderFieldName = orderedFields.get(i).getKey().toLowerCase();
final String indexFieldName = fields.get(i).toLowerCase();
if (!orderFieldName.equals(indexFieldName))
return false;
}
return true;
}
/**
* checks if, given a list of "=" conditions and a set of ORDER BY fields
*
* @param index
* @param equalsFilterFields
* @param orderedFields
* @return
*/
boolean canBeUsedByOrderByAfterFilter(OIndex<?> index, List<String> equalsFilterFields,
List<OPair<String, String>> orderedFields) {
if (orderedFields.isEmpty())
return false;
if (!index.supportsOrderedIterations())
return false;
final OIndexDefinition definition = index.getDefinition();
final List<String> indexFields = definition.getFields();
int endIndex = Math.min(indexFields.size(), equalsFilterFields.size());
final String firstOrder = orderedFields.get(0).getValue();
//check that all the "equals" clauses are a prefix for the index
for (int i = 0; i < endIndex; i++) {
final String equalsFieldName = equalsFilterFields.get(i).toLowerCase();
final String indexFieldName = indexFields.get(i).toLowerCase();
if (!equalsFieldName.equals(indexFieldName))
return false;
}
endIndex = Math.min(indexFields.size(), orderedFields.size() + equalsFilterFields.size());
if (endIndex == equalsFilterFields.size()) {
//the index is used only for filtering
return false;
}
//check that after that prefix there all the Order By fields in the right order
for (int i = equalsFilterFields.size(); i < endIndex; i++) {
int fieldOrderInOrderByClause = i - equalsFilterFields.size();
final OPair<String, String> pair = orderedFields.get(fieldOrderInOrderByClause);
if (!firstOrder.equals(pair.getValue()))
return false;
final String orderFieldName = pair.getKey().toLowerCase();
final String indexFieldName = indexFields.get(i).toLowerCase();
if (!orderFieldName.equals(indexFieldName))
return false;
}
return true;
}
}