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https://issues.apache.org/jira/browse/PARQUET-1977?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17288962#comment-17288962
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ASF GitHub Bot commented on PARQUET-1977:
-----------------------------------------
gszadovszky commented on a change in pull request #868:
URL: https://github.com/apache/parquet-mr/pull/868#discussion_r580868682
##########
File path: parquet-hadoop/src/main/java/org/apache/parquet/hadoop/Offsets.java
##########
@@ -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:
We do not have such field in the thrift file currently and even if we
add it it would not solve the issue of the already existing files. So, I guess
you've thought about adding an additional field to the parquet-mr side object
only to be set manually. To set it we need to read the dictionary which do not
do in the tools we currently use this functionality (mask/prune columns). But
the whole think is not a problem currently because we do not support
encryption/decryption in the tools anyway.
I am not sure if we want to support encryption in the tools later or it is
even feasible but for now it is correct as is. I'll remove the TODO line and
try to document the situation in the class header.
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> Invalid data_page_offset
> ------------------------
>
> Key: PARQUET-1977
> URL: https://issues.apache.org/jira/browse/PARQUET-1977
> Project: Parquet
> Issue Type: Bug
> Components: parquet-mr
> Affects Versions: 1.12.0
> Reporter: Gabor Szadovszky
> Assignee: Gabor Szadovszky
> Priority: Major
>
> The thrift field
> [{{data_page_offset}}|https://github.com/gszadovszky/parquet-format/blob/master/src/main/thrift/parquet.thrift#L733]
> is filled with incorrect value. Currently, it always points to the beginning
> of the column chunk which is not correct according to the spec in case there
> is a dictionary page. This is not a regression as it was written incorrectly
> since the beginning of parquet-mr.
> Meanwhile PARQUET-1850 fixed that we never wrote the field
> [{{dictionary_page_offset}}|https://github.com/gszadovszky/parquet-format/blob/master/src/main/thrift/parquet.thrift#L739].
> After the fix we correctly write this field if there is a dictionary filter.
> The problem is we are using the same value to fill both fields. So there are
> two possibilities:
> * There is no dictionary page in the column chunk so {{data_page_offset}} is
> filled with the correct value while {{dictionary_page_offset}} is not filled
> which is still correct. We are good.
> * There is a dictionary page at the beginning of the column chunk so
> {{data_page_offset}} and {{dictionary_page_offset}} are both contains the
> same value. This is not only a regression but it causes issues in other
> implementations (e.g. Impala) where footer validation is more strict than in
> parquet-mr because {{dictionary_page_offset}} shall be less than
> {{data_page_offset}} at all time if it is filled.
> So, we need to fill {{data_page_offset}} correctly.
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