[GitHub] [spark] sadikovi commented on a diff in pull request #36672: [SPARK-39265][SQL] Support vectorized Parquet scans with DEFAULT values

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

sadikovi commented on code in PR #36672:
URL: https://github.com/apache/spark/pull/36672#discussion_r885096588


##########
sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedParquetRecordReader.java:
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@@ -270,13 +271,40 @@ private void initBatch(
         vectors[i + partitionIdx].setIsConstant();
       }
     }
+
+    // For Parquet tables whose columns have associated DEFAULT values, this reader must return
+    // those values instead of NULL when the corresponding columns are not present in storage (i.e.
+    // belong to the 'missingColumns' field in this class).
+    ColumnVector[] finalColumns = new ColumnVector[sparkSchema.fields().length];
+    for (int i = 0; i < columnVectors.length; i++) {
+      Object defaultValue = sparkRequestedSchema.existenceDefaultValues()[i];
+      if (defaultValue == null) {
+        finalColumns[i] = vectors[i];
+      } else {
+        WritableColumnVector writable;
+        if (memMode == MemoryMode.OFF_HEAP) {
+          writable = new OffHeapColumnVector(capacity, vectors[i].dataType());

Review Comment:
   Could you elaborate how `appendObjects` replaces null values? Also, should we still preserve ColumnVector here instead of creating a new one?



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