| /* |
| * 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.phoenix.iterate; |
| |
| import java.sql.SQLException; |
| import java.util.List; |
| |
| import org.apache.hadoop.hbase.io.ImmutableBytesWritable; |
| import org.apache.phoenix.expression.Expression; |
| import org.apache.phoenix.expression.OrderByExpression; |
| import org.apache.phoenix.schema.tuple.Tuple; |
| |
| /** |
| * |
| * ResultIterator that does a merge sort on the list of iterators provided, |
| * returning the rows ordered by the OrderByExpression. The input |
| * iterators must be ordered by the OrderByExpression. |
| * |
| */ |
| public class MergeSortTopNResultIterator extends MergeSortResultIterator { |
| |
| private final int limit; |
| private int count = 0; |
| private int offsetCount = 0; |
| private final List<OrderByExpression> orderByColumns; |
| private final ImmutableBytesWritable ptr1 = new ImmutableBytesWritable(); |
| private final ImmutableBytesWritable ptr2 = new ImmutableBytesWritable(); |
| private final int offset; |
| |
| public MergeSortTopNResultIterator(ResultIterators iterators, Integer limit, Integer offset, |
| List<OrderByExpression> orderByColumns) { |
| super(iterators); |
| this.limit = limit == null ? -1 : limit; |
| this.offset = offset == null ? -1 : offset; |
| this.orderByColumns = orderByColumns; |
| } |
| |
| @Override |
| protected int compare(Tuple t1, Tuple t2) { |
| for (int i = 0; i < orderByColumns.size(); i++) { |
| OrderByExpression order = orderByColumns.get(i); |
| Expression orderExpr = order.getExpression(); |
| boolean isNull1 = !orderExpr.evaluate(t1, ptr1) || ptr1.getLength() == 0; |
| boolean isNull2 = !orderExpr.evaluate(t2, ptr2) || ptr2.getLength() == 0; |
| if (isNull1 && isNull2) { |
| continue; |
| } else if (isNull1) { |
| return order.isNullsLast() ? 1 : -1; |
| } else if (isNull2) { |
| return order.isNullsLast() ? -1 : 1; |
| } |
| int cmp = ptr1.compareTo(ptr2); |
| if (cmp == 0) { |
| continue; |
| } |
| return order.isAscending() ? cmp : -cmp; |
| } |
| return 0; |
| } |
| |
| @Override |
| public Tuple peek() throws SQLException { |
| while (offsetCount < offset) { |
| if (super.next() == null) { return null; } |
| offsetCount++; |
| } |
| if (limit >= 0 && count >= limit) { |
| return null; |
| } |
| return super.peek(); |
| } |
| |
| @Override |
| public Tuple next() throws SQLException { |
| while (offsetCount < offset) { |
| if (super.next() == null) { return null; } |
| offsetCount++; |
| } |
| if (limit >= 0 && count++ >= limit) { return null; } |
| return super.next(); |
| } |
| |
| |
| @Override |
| public void explain(List<String> planSteps) { |
| resultIterators.explain(planSteps); |
| planSteps.add("CLIENT MERGE SORT"); |
| if (offset > 0) { |
| planSteps.add("CLIENT OFFSET " + offset); |
| } |
| if (limit > 0) { |
| planSteps.add("CLIENT LIMIT " + limit); |
| } |
| } |
| |
| @Override |
| public String toString() { |
| return "MergeSortTopNResultIterator [limit=" + limit + ", count=" |
| + count + ", orderByColumns=" + orderByColumns + ", ptr1=" |
| + ptr1 + ", ptr2=" + ptr2 + ",offset=" + offset + "]"; |
| } |
| } |