| /* |
| * 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.store; |
| |
| import java.util.Collection; |
| import java.util.List; |
| import java.util.Map; |
| |
| import org.apache.drill.shaded.guava.com.google.common.collect.ImmutableList; |
| import org.apache.drill.common.expression.PathSegment; |
| import org.apache.drill.common.expression.SchemaPath; |
| import org.apache.drill.exec.exception.OutOfMemoryException; |
| import org.apache.drill.exec.physical.base.GroupScan; |
| import org.apache.drill.exec.util.Utilities; |
| import org.apache.drill.exec.vector.ValueVector; |
| |
| import org.apache.drill.shaded.guava.com.google.common.base.Preconditions; |
| |
| public abstract class AbstractRecordReader implements RecordReader { |
| private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(AbstractRecordReader.class); |
| |
| // For text reader, the default columns to read is "columns[0]". |
| protected static final List<SchemaPath> DEFAULT_TEXT_COLS_TO_READ = ImmutableList.of(new SchemaPath(new PathSegment.NameSegment("columns", new PathSegment.ArraySegment(0)))); |
| |
| private Collection<SchemaPath> columns = null; |
| private boolean isStarQuery = false; |
| private boolean isSkipQuery = false; |
| |
| @Override |
| public String toString() { |
| return super.toString() |
| + "[columns = " + columns |
| + ", isStarQuery = " + isStarQuery |
| + ", isSkipQuery = " + isSkipQuery + "]"; |
| } |
| |
| /** |
| * |
| * @param projected : The column list to be returned from this RecordReader. |
| * 1) empty column list: this is for skipAll query. It's up to each storage-plugin to |
| * choose different policy of handling skipAll query. By default, it will use * column. |
| * 2) NULL : is NOT allowed. It requires the planner's rule, or GroupScan or ScanBatchCreator to handle NULL. |
| */ |
| protected final void setColumns(Collection<SchemaPath> projected) { |
| Preconditions.checkNotNull(projected, Utilities.COL_NULL_ERROR); |
| isSkipQuery = projected.isEmpty(); |
| Collection<SchemaPath> columnsToRead = projected; |
| |
| // If no column is required (SkipQuery), by default it will use DEFAULT_COLS_TO_READ . |
| // Handling SkipQuery is storage-plugin specific : JSON, text reader, parquet will override, in order to |
| // improve query performance. |
| if (projected.isEmpty()) { |
| columnsToRead = getDefaultColumnsToRead(); |
| } |
| |
| isStarQuery = Utilities.isStarQuery(columnsToRead); |
| columns = transformColumns(columnsToRead); |
| |
| logger.debug("columns to read : {}", columns); |
| } |
| |
| protected Collection<SchemaPath> getColumns() { |
| return columns; |
| } |
| |
| protected Collection<SchemaPath> transformColumns(Collection<SchemaPath> projected) { |
| return projected; |
| } |
| |
| protected boolean isStarQuery() { |
| return isStarQuery; |
| } |
| |
| /** |
| * Returns true if reader should skip all of the columns, reporting number of records only. Handling of a skip query |
| * is storage plugin-specific. |
| */ |
| protected boolean isSkipQuery() { |
| return isSkipQuery; |
| } |
| |
| @Override |
| public void allocate(Map<String, ValueVector> vectorMap) throws OutOfMemoryException { |
| for (final ValueVector v : vectorMap.values()) { |
| v.allocateNew(); |
| } |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return false; |
| } |
| |
| protected List<SchemaPath> getDefaultColumnsToRead() { |
| return GroupScan.ALL_COLUMNS; |
| } |
| } |