| /** |
| * 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.metamodel.jdbc; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import org.apache.metamodel.DataContext; |
| import org.apache.metamodel.MetaModelHelper; |
| import org.apache.metamodel.data.DataSet; |
| import org.apache.metamodel.data.Row; |
| import org.apache.metamodel.query.FilterItem; |
| import org.apache.metamodel.query.FromClause; |
| import org.apache.metamodel.query.FromItem; |
| import org.apache.metamodel.query.FunctionType; |
| import org.apache.metamodel.query.GroupByItem; |
| import org.apache.metamodel.query.OperatorType; |
| import org.apache.metamodel.query.Query; |
| import org.apache.metamodel.query.SelectItem; |
| import org.apache.metamodel.schema.Column; |
| import org.apache.metamodel.schema.Table; |
| |
| /** |
| * The QuerySplitter class makes it possible to split up queries that are |
| * expected to yield a huge result set which may cause performance problems like |
| * OutOfMemoryError's or very long processing periods. The resulting queries |
| * will in union produce the same result, but in smaller bits (resultsets with |
| * less rows). |
| * |
| * Note that there is an initial performance-penalty associated with splitting |
| * the query since some queries will be executed in order to determine |
| * reasonable intervals to use for the resulting queries WHERE clauses. |
| * |
| * @see Query |
| * @see DataContext |
| */ |
| public final class QuerySplitter { |
| |
| public final static long DEFAULT_MAX_ROWS = 300000; |
| private static final int MINIMUM_MAX_ROWS = 100; |
| private final static Logger logger = LoggerFactory.getLogger(QuerySplitter.class); |
| |
| private final Query _query; |
| private final DataContext _dataContext; |
| private long _maxRows = DEFAULT_MAX_ROWS; |
| private Long _cachedRowCount = null; |
| |
| public QuerySplitter(DataContext dc, Query q) { |
| if (dc == null) { |
| throw new IllegalArgumentException("DataContext cannot be null"); |
| } |
| if (q == null) { |
| throw new IllegalArgumentException("Query cannot be null"); |
| } |
| _dataContext = dc; |
| _query = q; |
| } |
| |
| /** |
| * Splits the query into several queries that will together yield the same |
| * result set |
| * |
| * @return a list of queries that can be executed to yield the same |
| * collective result as this QuerySplitter's query |
| */ |
| public List<Query> splitQuery() { |
| List<Query> result = new ArrayList<Query>(); |
| if (isSplittable()) { |
| if (getRowCount() > _maxRows) { |
| Integer subQueryIndex = getSubQueryFromItemIndex(); |
| List<Query> splitQueries = null; |
| if (subQueryIndex != null) { |
| splitQueries = splitQueryBasedOnSubQueries(subQueryIndex); |
| } else { |
| List<Column> splitColumns = getSplitColumns(); |
| splitQueries = splitQueryBasedOnColumns(splitColumns); |
| } |
| result.addAll(splitQueries); |
| } else { |
| if (logger.isInfoEnabled()) { |
| logger.info("Accepted query, maxRows not exceeded: " + _query); |
| } |
| result.add(_query); |
| } |
| } |
| if (result.isEmpty()) { |
| logger.debug("Cannot further split query: {}", _query); |
| result.add(_query); |
| } |
| return result; |
| } |
| |
| private List<Query> splitQueryBasedOnColumns(List<Column> splitColumns) { |
| List<Query> result = new ArrayList<Query>(); |
| if (splitColumns.isEmpty() || getRowCount() <= _maxRows) { |
| if (getRowCount() > 0) { |
| result.add(_query); |
| } |
| } else { |
| Column firstColumn = splitColumns.get(0); |
| splitColumns.remove(0); |
| List<Query> splitQueries = splitQueryBasedOnColumn(firstColumn); |
| for (Query splitQuery : splitQueries) { |
| QuerySplitter qs = new QuerySplitter(_dataContext, splitQuery).setMaxRows(_maxRows); |
| if (qs.getRowCount() > _maxRows) { |
| // Recursively use the next columns to split queries |
| // subsequently |
| result.addAll(qs.splitQueryBasedOnColumns(splitColumns)); |
| } else { |
| if (qs.getRowCount() > 0) { |
| result.add(splitQuery); |
| } |
| } |
| } |
| } |
| return result; |
| } |
| |
| private List<Query> splitQueryBasedOnColumn(Column column) { |
| SelectItem maxItem = new SelectItem(FunctionType.MAX, column); |
| SelectItem minItem = new SelectItem(FunctionType.MIN, column); |
| Query q = new Query().from(column.getTable()).select(maxItem, minItem); |
| Row row = MetaModelHelper.executeSingleRowQuery(_dataContext, q); |
| long max = ceil((Number) row.getValue(maxItem)); |
| long min = floor((Number) row.getValue(minItem)); |
| long wholeRange = max - min; |
| List<Query> result = new ArrayList<Query>(); |
| if (wholeRange <= 1) { |
| result.add(_query); |
| } else { |
| long numSplits = ceil(getRowCount() / _maxRows); |
| if (numSplits < 2) { |
| // Must as a minimum yield two new queries |
| numSplits = 2; |
| } |
| int splitInterval = (int) (wholeRange / numSplits); |
| for (int i = 0; i < numSplits; i++) { |
| q = _query.clone(); |
| long lowLimit = min + (i * splitInterval); |
| long highLimit = lowLimit + splitInterval; |
| |
| FilterItem lowerThanFilter = new FilterItem(new SelectItem(column), OperatorType.LESS_THAN, highLimit); |
| FilterItem higherThanFilter = new FilterItem(new SelectItem(column), OperatorType.GREATER_THAN, |
| lowLimit); |
| FilterItem equalsFilter = new FilterItem(new SelectItem(column), OperatorType.EQUALS_TO, lowLimit); |
| |
| if (i == 0) { |
| // This is the first split query: no higherThan filter and |
| // include |
| // IS NULL |
| FilterItem nullFilter = new FilterItem(new SelectItem(column), OperatorType.EQUALS_TO, null); |
| FilterItem orFilterItem = new FilterItem(lowerThanFilter, nullFilter); |
| q.where(orFilterItem); |
| } else if (i + 1 == numSplits) { |
| // This is the lats split query: no lowerThan filter, |
| FilterItem orFilterItem = new FilterItem(higherThanFilter, equalsFilter); |
| q.where(orFilterItem); |
| } else { |
| higherThanFilter = new FilterItem(higherThanFilter, equalsFilter); |
| lowerThanFilter = new FilterItem(lowerThanFilter, equalsFilter); |
| q.where(higherThanFilter); |
| q.where(lowerThanFilter); |
| } |
| result.add(q); |
| } |
| } |
| return result; |
| } |
| |
| private static long floor(Number value) { |
| Double floor = Math.floor(value.doubleValue()); |
| return floor.longValue(); |
| } |
| |
| private static long ceil(Number value) { |
| Double ceil = Math.ceil(value.doubleValue()); |
| return ceil.longValue(); |
| } |
| |
| private List<Query> splitQueryBasedOnSubQueries(int fromItemIndex) { |
| Query subQuery = _query.getFromClause().getItem(fromItemIndex).getSubQuery(); |
| QuerySplitter subQuerySplitter = new QuerySplitter(_dataContext, subQuery); |
| |
| subQuerySplitter.setMaxRows(_maxRows); |
| List<Query> splitQueries = subQuerySplitter.splitQuery(); |
| List<Query> result = new ArrayList<Query>(splitQueries.size()); |
| for (Query splitQuery : splitQueries) { |
| Query newQuery = _query.clone(); |
| FromClause fromClause = newQuery.getFromClause(); |
| String alias = fromClause.getItem(fromItemIndex).getAlias(); |
| fromClause.removeItem(fromItemIndex); |
| newQuery.from(new FromItem(splitQuery).setAlias(alias)); |
| result.add(newQuery); |
| } |
| return result; |
| } |
| |
| private Integer getSubQueryFromItemIndex() { |
| List<FromItem> fromItems = _query.getFromClause().getItems(); |
| for (int i = 0; i < fromItems.size(); i++) { |
| Query subQuery = fromItems.get(i).getSubQuery(); |
| if (subQuery != null) { |
| if (isSplittable(subQuery)) { |
| return i; |
| } |
| } |
| } |
| return null; |
| } |
| |
| private boolean isSplittable() { |
| return isSplittable(_query); |
| } |
| |
| public static boolean isSplittable(Query q) { |
| if (q.getOrderByClause().getItemCount() != 0) { |
| return false; |
| } |
| return true; |
| } |
| |
| private List<Column> getSplitColumns() { |
| List<Column> result = new ArrayList<Column>(); |
| if (_query.getGroupByClause().getItemCount() != 0) { |
| List<GroupByItem> groupByItems = _query.getGroupByClause().getItems(); |
| for (GroupByItem groupByItem : groupByItems) { |
| Column column = groupByItem.getSelectItem().getColumn(); |
| if (column != null) { |
| if (column.isIndexed()) { |
| // Indexed columns have first priority, they will be |
| // added to the beginning of the list |
| result.add(0, column); |
| } else { |
| result.add(column); |
| } |
| } |
| } |
| } else { |
| List<FromItem> fromItems = _query.getFromClause().getItems(); |
| for (FromItem fromItem : fromItems) { |
| if (fromItem.getTable() != null) { |
| addColumnsToResult(fromItem.getTable(), result); |
| } |
| if (fromItem.getJoin() != null && fromItem.getAlias() == null) { |
| if (fromItem.getLeftSide().getTable() != null) { |
| addColumnsToResult(fromItem.getLeftSide().getTable(), result); |
| } |
| if (fromItem.getRightSide().getTable() != null) { |
| addColumnsToResult(fromItem.getRightSide().getTable(), result); |
| } |
| } |
| } |
| } |
| return result; |
| } |
| |
| private static void addColumnsToResult(Table table, List<Column> result) { |
| Column[] numberColumns = table.getNumberColumns(); |
| for (int i = 0; i < numberColumns.length; i++) { |
| Column column = numberColumns[i]; |
| if (column.isIndexed()) { |
| // Indexed columns have first priority, they will be |
| // added to the beginning of the list |
| result.add(0, column); |
| } else { |
| result.add(column); |
| } |
| } |
| } |
| |
| /** |
| * @return the total number of rows expected from executing the query. |
| */ |
| public long getRowCount() { |
| if (_cachedRowCount == null) { |
| _cachedRowCount = getRowCount(_query); |
| } |
| return _cachedRowCount; |
| } |
| |
| private long getRowCount(Query q) { |
| q = q.clone(); |
| SelectItem countAllItem = SelectItem.getCountAllItem(); |
| if (q.getGroupByClause().getItemCount() > 0) { |
| q = new Query().from(new FromItem(q).setAlias("sq")).select(countAllItem); |
| } else { |
| q.getSelectClause().removeItems(); |
| q.select(countAllItem); |
| } |
| Row row = MetaModelHelper.executeSingleRowQuery(_dataContext, q); |
| Number count = (Number) row.getValue(countAllItem); |
| return count.longValue(); |
| } |
| |
| /** |
| * Sets the desired maximum result set row count. Note that this size cannot |
| * be guaranteed, but will serve as an indicator for determining the |
| * split-size |
| * |
| * @param maxRows |
| */ |
| public QuerySplitter setMaxRows(long maxRows) { |
| if (maxRows < MINIMUM_MAX_ROWS) { |
| throw new IllegalArgumentException("maxRows must be higher than " + MINIMUM_MAX_ROWS); |
| } |
| _maxRows = maxRows; |
| return this; |
| } |
| |
| public DataSet executeQueries() { |
| return executeQueries(splitQuery()); |
| } |
| |
| public DataSet executeQueries(List<Query> splitQueries) { |
| return new SplitQueriesDataSet(_dataContext, splitQueries); |
| } |
| } |