[GitHub] [parquet-mr] ggershinsky commented on a change in pull request #868: PARQUET-1977: Invalid data_page_offset

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

ggershinsky commented on a change in pull request #868:
URL: https://github.com/apache/parquet-mr/pull/868#discussion_r580860001



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File path: parquet-hadoop/src/main/java/org/apache/parquet/hadoop/Offsets.java
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@@ -0,0 +1,84 @@
+/*
+ * 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.parquet.hadoop;
+
+import java.io.IOException;
+
+import org.apache.parquet.format.PageHeader;
+import org.apache.parquet.format.Util;
+import org.apache.parquet.hadoop.metadata.ColumnChunkMetaData;
+import org.apache.parquet.io.SeekableInputStream;
+
+/**
+ * Class to help gather/calculate the proper values of the dictionary/first data page offset values in a column chunk.
+ */
+class Offsets {
+
+  /**
+   * Returns the offset values for the column chunk to be written.
+   *
+   * @param input         the source input stream of the column chunk
+   * @param chunk         the column chunk metadata read from the source file
+   * @param newChunkStart the position of the column chunk to be written
+   * @return the offset values
+   * @throws IOException if any I/O error occurs during the reading of the input stream
+   */
+  public static Offsets getOffsets(SeekableInputStream input, ColumnChunkMetaData chunk, long newChunkStart)
+      throws IOException {
+    long firstDataPageOffset;
+    long dictionaryPageOffset;
+    if (chunk.hasDictionaryPage()) {
+      long dictionaryPageSize = chunk.getFirstDataPageOffset() - chunk.getDictionaryPageOffset();
+      if (dictionaryPageSize <= 0) {
+        // The offset values might be invalid so we have to read the size of the dictionary page
+        dictionaryPageSize = readDictionaryPageSize(input, newChunkStart);
+      }
+      firstDataPageOffset = newChunkStart + dictionaryPageSize;
+      dictionaryPageOffset = newChunkStart;
+    } else {
+      firstDataPageOffset = newChunkStart;
+      dictionaryPageOffset = 0;
+    }
+    return new Offsets(firstDataPageOffset, dictionaryPageOffset);
+  }
+
+  private static long readDictionaryPageSize(SeekableInputStream in, long pos) throws IOException {
+    long origPos = -1;
+    try {
+      origPos = in.getPos();
+      // TODO: Do we need to handle encryption here?

Review comment:
       Setting up decryption in the writer could be a major headache. Would it be possible to store the dictionary page size in the `ColumnChunkMetaData chunk` object?




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