| /* |
| * 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.drill.exec.physical.resultSet.impl; |
| |
| import org.apache.drill.exec.physical.resultSet.ResultSetLoader; |
| import org.apache.drill.exec.vector.ValueVector; |
| import org.apache.drill.exec.vector.accessor.ColumnWriterIndex; |
| |
| /** |
| * Writer index that points to each row in the row set. The index starts at |
| * the 0th row and advances one row on each increment. This allows writers to |
| * start positioned at the first row. Writes happen in the current row. |
| * Calling <tt>next()</tt> advances to the next position, effectively saving |
| * the current row. The most recent row can be abandoned easily simply by not |
| * calling <tt>next()</tt>. This means that the number of completed rows is |
| * the same as the row index. |
| * <p> |
| * The writer index enforces the row count limit for a new batch. The |
| * limit is set by the result set loader and can vary from batch to batch |
| * if the client chooses in order to adjust the row count based on actual |
| * data size. |
| */ |
| |
| class WriterIndexImpl implements ColumnWriterIndex { |
| |
| private final ResultSetLoader rsLoader; |
| private int rowIndex; |
| |
| public WriterIndexImpl(ResultSetLoader rsLoader) { |
| this.rsLoader = rsLoader; |
| } |
| |
| @Override |
| public int vectorIndex() { return rowIndex; } |
| |
| @Override |
| public int rowStartIndex() { return rowIndex; } |
| |
| public boolean next() { |
| if (++rowIndex < rsLoader.targetRowCount()) { |
| return true; |
| } else { |
| // Should not call next() again once batch is full. |
| rowIndex = rsLoader.targetRowCount(); |
| return false; |
| } |
| } |
| |
| public int skipRows(int requestedCount) { |
| |
| // Determine the number of rows that can be skipped. Note that since the |
| // batch must have no columns, there is no need to observe the normal |
| // batch size limit. |
| |
| int skipped = Math.min(requestedCount, |
| ValueVector.MAX_ROW_COUNT - rowIndex); |
| |
| // Update the row index with the skip count. |
| |
| rowIndex += skipped; |
| |
| // Tell the client how many rows were actually skipped. |
| // The client can make more requests in later batches to get |
| // the full amount. |
| |
| return skipped; |
| } |
| |
| public int size() { |
| |
| // The index always points to the next slot past the |
| // end of valid rows. |
| |
| return rowIndex; |
| } |
| |
| public boolean valid() { return rowIndex < rsLoader.targetRowCount(); } |
| |
| @Override |
| public void rollover() { |
| |
| // The top level index always rolls over to 0 -- |
| // the first row position in the new vectors. |
| |
| reset(); |
| } |
| |
| public void reset() { rowIndex = 0; } |
| |
| @Override |
| public void nextElement() { } |
| |
| @Override |
| public void prevElement() { } |
| |
| @Override |
| public ColumnWriterIndex outerIndex() { return null; } |
| |
| @Override |
| public String toString() { |
| return new StringBuilder() |
| .append("[") |
| .append(getClass().getSimpleName()) |
| .append(" rowIndex = ") |
| .append(rowIndex) |
| .append("]") |
| .toString(); |
| } |
| } |