[GitHub] [incubator-pinot] Jackie-Jiang commented on a change in pull request #6997: Add genericRow file reader and writer

[GitBox <gi...@apache.org>]

Jackie-Jiang commented on a change in pull request #6997:
URL: https://github.com/apache/incubator-pinot/pull/6997#discussion_r641166681



##########
File path: pinot-core/src/main/java/org/apache/pinot/core/segment/processing/genericrow/GenericRowFileReader.java
##########
@@ -0,0 +1,85 @@
+/**
+ * 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.pinot.core.segment.processing.genericrow;
+
+import java.io.Closeable;
+import java.io.File;
+import java.io.IOException;
+import java.nio.ByteOrder;
+import java.util.List;
+import org.apache.pinot.segment.spi.memory.PinotDataBuffer;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+
+
+/**
+ * File reader for {@link GenericRow}. The input files should be generated by the {@link GenericRowFileWriter}.
+ */
+public class GenericRowFileReader implements Closeable {
+  private final int _numRows;
+  private final PinotDataBuffer _offsetBuffer;
+  private final PinotDataBuffer _dataBuffer;
+  private final GenericRowDeserializer _deserializer;
+
+  public GenericRowFileReader(File offsetFile, File dataFile, List<FieldSpec> fieldSpecs, boolean includeNullFields)
+      throws IOException {
+    long offsetFileLength = offsetFile.length();
+    _numRows = (int) (offsetFileLength >>> 3);
+    _offsetBuffer = PinotDataBuffer
+        .mapFile(offsetFile, true, 0L, offsetFileLength, ByteOrder.BIG_ENDIAN, "GenericRow offset buffer");
+    _dataBuffer = PinotDataBuffer
+        .mapFile(dataFile, true, 0L, dataFile.length(), PinotDataBuffer.NATIVE_ORDER, "GenericRow data buffer");
+    _deserializer = new GenericRowDeserializer(_dataBuffer, fieldSpecs, includeNullFields);
+  }
+
+  /**
+   * Returns the number of rows within the files.
+   */
+  public int getNumRows() {
+    return _numRows;
+  }
+
+  /**
+   * Reads the data of the given row id into the given reusable row.
+   */
+  public GenericRow read(int rowId, GenericRow reuse) {
+    long offset = _offsetBuffer.getLong((long) rowId << 3);
+    try {
+      _deserializer.deserialize(offset, reuse);
+    } catch (Exception e) {
+      System.out.println();

Review comment:
       Good catch! Forgot it while debugging :-(




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