[GitHub] [hive] jdere commented on a change in pull request #791: HIVE-21924

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

jdere commented on a change in pull request #791: HIVE-21924
URL: https://github.com/apache/hive/pull/791#discussion_r331316286
 
 

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 File path: ql/src/java/org/apache/hadoop/hive/ql/io/SkippingTextInputFormat.java
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 @@ -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);
 
 Review comment:
   Some comments here might be useful

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