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

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

rdsr commented on a change in pull request #199: ORC metrics
URL: https://github.com/apache/incubator-iceberg/pull/199#discussion_r293663179
 
 

 ##########
 File path: orc/src/main/java/org/apache/iceberg/orc/OrcMetrics.java
 ##########
 @@ -45,16 +61,82 @@ public static Metrics fromInputFile(InputFile file, Configuration config) {
     try {
       final Reader orcReader = OrcFile.createReader(new Path(file.location()),
           OrcFile.readerOptions(config));
+      final Schema schema = TypeConversion.fromOrc(orcReader.getSchema());
+
+      ColumnStatistics[] colStats = orcReader.getStatistics();
+      Map<Integer, Long> columSizes = Maps.newHashMapWithExpectedSize(colStats.length);
+      Map<Integer, Long> valueCounts = Maps.newHashMapWithExpectedSize(colStats.length);
+      Map<Integer, ByteBuffer> lowerBounds = Maps.newHashMap();
+      Map<Integer, ByteBuffer> upperBounds = Maps.newHashMap();
+
+      for(Types.NestedField col : schema.columns()) {
+        final int i = col.fieldId();
+        columSizes.put(i, colStats[i].getBytesOnDisk());
+        valueCounts.put(i, colStats[i].getNumberOfValues());
+
+        Optional<ByteBuffer> orcMin = fromOrcMin(col, colStats[i]);
+        orcMin.ifPresent(byteBuffer -> lowerBounds.put(i, byteBuffer));
+        Optional<ByteBuffer> orcMax = fromOrcMax(col, colStats[i]);
+        orcMax.ifPresent(byteBuffer -> upperBounds.put(i, byteBuffer));
+      }
 
-      // TODO: implement rest of the methods for ORC metrics
       return new Metrics(orcReader.getNumberOfRows(),
-          null,
-          null,
+          columSizes,
+          valueCounts,
           Collections.emptyMap(),
-          null,
-          null);
+          lowerBounds,
+          upperBounds);
     } catch (IOException ioe) {
       throw new RuntimeIOException(ioe, "Failed to read footer of file: %s", file);
     }
   }
+
+  private static Optional<ByteBuffer> fromOrcMin(Types.NestedField column,
+                                                 ColumnStatistics columnStats) {
+    ByteBuffer min = null;
+    if (columnStats instanceof IntegerColumnStatistics) {
+      IntegerColumnStatistics intColStats = (IntegerColumnStatistics) columnStats;
+      if (column.type().typeId() == Type.TypeID.INTEGER) {
+        min = toByteBuffer(column.type(), (int) intColStats.getMinimum());
+      } else {
+        min = toByteBuffer(column.type(), intColStats.getMinimum());
+      }
+    } else if (columnStats instanceof DoubleColumnStatistics) {
+      min = toByteBuffer(column.type(), ((DoubleColumnStatistics) columnStats).getMinimum());
+    } else if (columnStats instanceof StringColumnStatistics) {
+      min = toByteBuffer(column.type(), ((StringColumnStatistics) columnStats).getMinimum());
 
 Review comment:
   I just hit this exception. 
   `
   java.lang.NullPointerException
     at java.nio.CharBuffer.wrap(CharBuffer.java:487)
     at org.apache.iceberg.types.Conversions.toByteBuffer(Conversions.java:96)
     at org.apache.iceberg.orc.OrcMetrics.fromOrcMin(OrcMetrics.java:107)
     at org.apache.iceberg.orc.OrcMetrics.fromInputFile(OrcMetrics.java:77)
     at org.apache.iceberg.orc.OrcMetrics.fromInputFile(OrcMetrics.java:57)
   `
   Seems like StringColumnstatistics can return null for min/max .  What other non-primitive columns can return null for min/max?

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