org.apache.drill.exec.store.AbstractRecordReader.java Source code

Introduction

Here is the source code for org.apache.drill.exec.store.AbstractRecordReader.java

Source

/**
 * 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.Map;

import org.apache.drill.common.expression.SchemaPath;
import org.apache.drill.exec.memory.OutOfMemoryException;
import org.apache.drill.exec.planner.logical.ColumnList;
import org.apache.drill.exec.record.MaterializedField.Key;
import org.apache.drill.exec.vector.ValueVector;

import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;

public abstract class AbstractRecordReader implements RecordReader {
    private static final String COL_NULL_ERROR = "Columns cannot be null. Use star column to select all fields.";
    private static final String COL_EMPTY_ERROR = "Readers needs at least a column to read.";
    public static final SchemaPath STAR_COLUMN = SchemaPath.getSimplePath("*");

    private Collection<SchemaPath> columns = null;
    private boolean isStarQuery = false;
    private boolean isSkipQuery = false;

    protected final void setColumns(Collection<SchemaPath> projected) {
        assert Preconditions.checkNotNull(projected, COL_NULL_ERROR).size() > 0 : COL_EMPTY_ERROR;
        if (projected instanceof ColumnList) {
            final ColumnList columns = ColumnList.class.cast(projected);
            isSkipQuery = columns.getMode() == ColumnList.Mode.SKIP_ALL;
        }
        isStarQuery = isStarQuery(projected);
        columns = transformColumns(projected);
    }

    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;
    }

    public static boolean isStarQuery(Collection<SchemaPath> projected) {
        return Iterables
                .tryFind(Preconditions.checkNotNull(projected, COL_NULL_ERROR), new Predicate<SchemaPath>() {
                    @Override
                    public boolean apply(SchemaPath path) {
                        return Preconditions.checkNotNull(path).equals(STAR_COLUMN);
                    }
                }).isPresent();
    }

    @Override
    public void allocate(Map<Key, ValueVector> vectorMap) throws OutOfMemoryException {
        for (ValueVector v : vectorMap.values()) {
            v.allocateNew();
        }
    }
}