[GitHub] [incubator-iceberg] rdsr commented on a change in pull request #199: ORC metrics and listPartition support

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

rdsr commented on a change in pull request #199: ORC metrics and listPartition support
URL: https://github.com/apache/incubator-iceberg/pull/199#discussion_r288349511
 
 

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 File path: orc/src/main/java/org/apache/iceberg/orc/OrcMetrics.java
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 @@ -0,0 +1,162 @@
+/*
+ * 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.iceberg.orc;
+
+import com.google.common.collect.Maps;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Path;
+import org.apache.iceberg.Metrics;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.exceptions.RuntimeIOException;
+import org.apache.iceberg.expressions.Literal;
+import org.apache.iceberg.hadoop.HadoopInputFile;
+import org.apache.iceberg.io.InputFile;
+import org.apache.iceberg.types.Conversions;
+import org.apache.iceberg.types.Type;
+import org.apache.iceberg.types.Types;
+import org.apache.orc.ColumnStatistics;
+import org.apache.orc.OrcFile;
+import org.apache.orc.OrcProto;
+import org.apache.orc.Reader;
+import org.apache.orc.TypeDescription;
+
+public class OrcMetrics {
+
+  private OrcMetrics() {}
+
+  public static Metrics fromInputFile(InputFile file) {
+    final Configuration config = (file instanceof HadoopInputFile)
+        ? ((HadoopInputFile)file).getConf()
+        : new Configuration();
+    return fromInputFile(file, config);
+  }
+
+  public static Metrics fromInputFile(InputFile file, Configuration config) {
+    try {
+      final Reader orcReader = OrcFile.createReader(new Path(file.location()),
+          OrcFile.readerOptions(config));
+      final TypeDescription orcSchema = orcReader.getSchema();
+      final Schema schema = TypeConversion.fromOrc(orcSchema);
+
+      ColumnStatistics[] colStats = orcReader.getStatistics();
+      List<OrcProto.ColumnStatistics> colStatsProto = orcReader.getOrcProtoFileStatistics();
+      Map<Integer, Long> columSizes = Maps.newHashMapWithExpectedSize(colStats.length);
+      Map<Integer, Long> valueCounts = Maps.newHashMapWithExpectedSize(colStats.length);
+      Map<Integer, Literal<?>> lowerBounds = Maps.newHashMap();
+      Map<Integer, Literal<?>> upperBounds = Maps.newHashMap();
+
+      for (int i = 0; i < colStats.length; i++) {
+        columSizes.put(i, colStats[i].getBytesOnDisk());
+        valueCounts.put(i, colStats[i].getNumberOfValues());
+
+        final OrcProto.ColumnStatistics protoStats = colStatsProto.get(i);
+        final Types.NestedField col = schema.findField(i);
+        if (col != null) {
+          Optional<Literal<?>> orcMin = fromOrcMin(col, protoStats);
+          if (orcMin.isPresent()) {
+            lowerBounds.put(i, orcMin.get());
+          }
+          Optional<Literal<?>> orcMax = fromOrcMax(col, protoStats);
+          if (orcMax.isPresent()) {
+            upperBounds.put(i, orcMax.get());
+          }
+        }
+      }
+
+      return new Metrics(orcReader.getNumberOfRows(),
+          columSizes,
+          valueCounts,
+          Maps.newHashMap(),
+          toBufferMap(schema, lowerBounds),
+          toBufferMap(schema, upperBounds));
+    } catch (IOException ioe) {
+      throw new RuntimeIOException(ioe, "Failed to read footer of file: %s", file);
+    }
+  }
+
+  private static Optional<Literal<?>> fromOrcMin(Types.NestedField column,
+                                                    OrcProto.ColumnStatistics columnStats) {
+    Literal<?> min = null;
+    if (columnStats.hasIntStatistics()) {
+      if (column.type().typeId() == Type.TypeID.INTEGER) {
+        min = Literal.of((int) columnStats.getIntStatistics().getMinimum());
 
 Review comment:
   Why convert to bytebuffers in a separate function? It seems that if we do it here itself, we save traversing the columns again and possibly also simplify the code a little.
   e.g instead of 
   `Literal.of(columnStats.getDoubleStatistics().getMaximum());` we could do 
   ` Conversions.toByteBuffer(column.type(), columnStats.getDoubleStatistics().getMinimum());`
     

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