/**
* 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.parquet.columnreaders;
import org.apache.drill.common.exceptions.ExecutionSetupException;
import org.apache.drill.exec.vector.BitVector;
import org.apache.parquet.column.ColumnDescriptor;
import org.apache.parquet.format.SchemaElement;
import org.apache.parquet.hadoop.metadata.ColumnChunkMetaData;
final class BitReader extends ColumnReader<BitVector> {
BitReader(ParquetRecordReader parentReader, int allocateSize, ColumnDescriptor descriptor, ColumnChunkMetaData columnChunkMetaData,
boolean fixedLength, BitVector v, SchemaElement schemaElement) throws ExecutionSetupException {
super(parentReader, allocateSize, descriptor, columnChunkMetaData, fixedLength, v, schemaElement);
}
@Override
protected void readField(long recordsToReadInThisPass) {
recordsReadInThisIteration = Math.min(pageReader.currentPageCount
- pageReader.valuesRead, recordsToReadInThisPass - valuesReadInCurrentPass);
// A more optimized reader for bit columns was removed to fix the bug
// DRILL-2031. It attempted to copy large runs of values directly from the
// decompressed parquet stream into a BitVector. This was complicated by
// parquet not always breaking a page on a row number divisible by 8. In
// this case the batch would have to be cut off early or we would have to
// copy the next page byte-by-byte with a bit shift to move the values into
// the correct position (to make the value vector one contiguous buffer of
// data). As page boundaries do not line up across columns, cutting off a
// batch at every page boundary of a bit column could be costly with many
// such pages, so we opted to try to shift the bits when necessary.
//
// In the end, this was too much complexity for not enough performance
// benefit, for now this reader has been moved to use the higher level value
// by value reader provided by the parquet library.
for (int i = 0; i < recordsReadInThisIteration; i++){
valueVec.getMutator().setSafe(i + valuesReadInCurrentPass,
pageReader.valueReader.readBoolean() ? 1 : 0 );
}
}
}