[
https://issues.apache.org/jira/browse/HIVE-21924?focusedWorklogId=323194&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-323194
]
ASF GitHub Bot logged work on HIVE-21924:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 04/Oct/19 05:33
Start Date: 04/Oct/19 05:33
Worklog Time Spent: 10m
Work Description: sankarh commented on pull request #791: HIVE-21924
URL: https://github.com/apache/hive/pull/791#discussion_r331338984
##########
File path:
ql/src/java/org/apache/hadoop/hive/ql/io/SkippingTextInputFormat.java
##########
@@ -0,0 +1,212 @@
+/*
+ * 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.hadoop.hive.ql.io;
+
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.mapred.FileSplit;
+import org.apache.hadoop.mapred.JobConf;
+import org.apache.hadoop.mapred.TextInputFormat;
+
+import java.io.IOException;
+import java.util.ArrayDeque;
+import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * SkippingInputFormat is a header/footer aware input format. It truncates
+ * splits identified by TextInputFormat. Header and footers are removed
+ * from the splits.
+ */
+public class SkippingTextInputFormat extends TextInputFormat {
+
+ private final Map<Path, Long> startIndexMap = new ConcurrentHashMap<Path,
Long>();
+ private final Map<Path, Long> endIndexMap = new ConcurrentHashMap<Path,
Long>();
+ private JobConf conf;
+ private int headerCount;
+ private int footerCount;
+
+ @Override
+ public void configure(JobConf conf) {
+ this.conf = conf;
+ super.configure(conf);
+ }
+
+ public void configure(JobConf conf, int headerCount, int footerCount) {
+ configure(conf);
+ this.headerCount = headerCount;
+ this.footerCount = footerCount;
+ }
+
+ @Override
+ protected FileSplit makeSplit(Path file, long start, long length, String[]
hosts) {
+ return makeSplitInternal(file, start, length, hosts, null);
+ }
+
+ @Override
+ protected FileSplit makeSplit(Path file, long start, long length, String[]
hosts, String[] inMemoryHosts) {
+ return makeSplitInternal(file, start, length, hosts, inMemoryHosts);
+ }
+
+ private FileSplit makeSplitInternal(Path file, long start, long length,
String[] hosts, String[] inMemoryHosts) {
+ long cachedStart;
+ long cachedEnd;
+ try {
+ cachedStart = getCachedStartIndex(file);
+ cachedEnd = getCachedEndIndex(file);
+ } catch (IOException e) {
+ LOG.warn("Could not detect header/footer", e);
+ return new NullRowsInputFormat.DummyInputSplit(file);
+ }
+ if (cachedStart > start + length) {
+ return new NullRowsInputFormat.DummyInputSplit(file);
+ }
+ if (cachedStart > start) {
+ length = length - (cachedStart - start);
+ start = cachedStart;
+ }
+ if (cachedEnd < start) {
+ return new NullRowsInputFormat.DummyInputSplit(file);
+ }
+ if (cachedEnd < start + length) {
+ length = cachedEnd - start;
+ }
+ if (inMemoryHosts == null) {
+ return super.makeSplit(file, start, length, hosts);
+ } else {
+ return super.makeSplit(file, start, length, hosts, inMemoryHosts);
+ }
+ }
+
+ private long getCachedStartIndex(Path path) throws IOException {
+ if (headerCount == 0) {
+ return 0;
+ }
+ Long startIndexForFile = startIndexMap.get(path);
+ if (startIndexForFile == null) {
+ FileSystem fileSystem;
+ FSDataInputStream fis = null;
+ fileSystem = path.getFileSystem(conf);
+ try {
+ fis = fileSystem.open(path);
+ for (int j = 0; j < headerCount; j++) {
+ if (fis.readLine() == null) {
+ startIndexMap.put(path, Long.MAX_VALUE);
+ return Long.MAX_VALUE;
+ }
+ }
+ // back 1 byte because readers skip the entire first row if split
start is not 0
+ startIndexForFile = fis.getPos() - 1;
+ } finally {
+ if (fis != null) {
+ fis.close();
+ }
+ }
+ startIndexMap.put(path, startIndexForFile);
+ }
+ return startIndexForFile;
+ }
+
+ private long getCachedEndIndex(Path path) throws IOException {
+ Long endIndexForFile = endIndexMap.get(path);
+ if (endIndexForFile == null) {
+ final long bufferSectionSize = 5 * 1024;
+ FileSystem fileSystem = path.getFileSystem(conf);
+ long endOfFile = fileSystem.getFileStatus(path).getLen();
+ if (footerCount == 0) {
+ endIndexForFile = endOfFile;
+ } else {
+ long bufferSectionEnd = endOfFile;
+ long bufferSectionStart = Math.max(0, bufferSectionEnd -
bufferSectionSize);
Review comment:
Small optimization: If we already know the valid startIdx after header
rows(from startIndexMap), then we shall use it as bufferSectionStart if above
line returns lesser value.
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Issue Time Tracking
-------------------
Worklog Id: (was: 323194)
Time Spent: 1h 50m (was: 1h 40m)
> Split text files even if header/footer exists
> ---------------------------------------------
>
> Key: HIVE-21924
> URL: https://issues.apache.org/jira/browse/HIVE-21924
> Project: Hive
> Issue Type: Improvement
> Components: File Formats
> Affects Versions: 2.4.0, 4.0.0, 3.2.0
> Reporter: Prasanth Jayachandran
> Assignee: Mustafa Iman
> Priority: Major
> Labels: pull-request-available
> Attachments: HIVE-21924.2.patch, HIVE-21924.3.patch,
> HIVE-21924.4.patch, HIVE-21924.patch
>
> Time Spent: 1h 50m
> Remaining Estimate: 0h
>
> https://github.com/apache/hive/blob/967a1cc98beede8e6568ce750ebeb6e0d048b8ea/ql/src/java/org/apache/hadoop/hive/ql/io/HiveInputFormat.java#L494-L503
>
> {code}
> int headerCount = 0;
> int footerCount = 0;
> if (table != null) {
> headerCount = Utilities.getHeaderCount(table);
> footerCount = Utilities.getFooterCount(table, conf);
> if (headerCount != 0 || footerCount != 0) {
> // Input file has header or footer, cannot be splitted.
> HiveConf.setLongVar(conf, ConfVars.MAPREDMINSPLITSIZE,
> Long.MAX_VALUE);
> }
> }
> {code}
> this piece of code makes the CSV (or any text files with header/footer) files
> not splittable if header or footer is present.
> If only header is present, we can find the offset after first line break and
> use that to split. Similarly for footer, may be read few KB's of data at the
> end and find the last line break offset. Use that to determine the data range
> which can be used for splitting. Few reads during split generation are
> cheaper than not splitting the file at all.
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