Fix Parquet V2 page reading when max def/rep levels are 0 (facebookin…

…cubator#9939)

Summary:
The existing code did not skip the definition and repetition level arrays if the `maxDefine_` and `maxRepeat_` are both zero but these arrays were actually more than 0 bytes. This commit fixes this problem and always uses `pageHeader.data_page_header_v2.definition_levels_byte_length` and `pageHeader.data_page_header_v2.repetition_levels_byte_length` as the array lengths because these values are guaranteed to exist.

Fixes facebookincubator#9924

Pull Request resolved: facebookincubator#9939

Reviewed By: pedroerp

Differential Revision: D57975496

Pulled By: Yuhta

fbshipit-source-id: d9a8dde1973942a3b9cc5212db24e38c2ff3983d

velox/dwio/parquet/reader/PageReader.cpp

@@ -261,12 +261,11 @@ void PageReader::prepareDataPageV2(const PageHeader& pageHeader, int64_t row) {
     return;
   }
 
-  uint32_t defineLength = maxDefine_ > 0
-      ? pageHeader.data_page_header_v2.definition_levels_byte_length
-      : 0;
-  uint32_t repeatLength = maxRepeat_ > 0
-      ? pageHeader.data_page_header_v2.repetition_levels_byte_length
-      : 0;
+  uint32_t defineLength =
+      pageHeader.data_page_header_v2.definition_levels_byte_length;
+  uint32_t repeatLength =
+      pageHeader.data_page_header_v2.repetition_levels_byte_length;
+
   auto bytes = pageHeader.compressed_page_size;
   pageData_ = readBytes(bytes, pageBuffer_);
 

velox/dwio/parquet/tests/reader/ParquetReaderTest.cpp

@@ -1156,3 +1156,28 @@ TEST_F(ParquetReaderTest, readVarbinaryFromFLBA) {
       result->as<RowVector>()->childAt(0)->asFlatVector<StringView>()->valueAt(
           0));
 }
+
+TEST_F(ParquetReaderTest, testV2PageWithZeroMaxDefRep) {
+  // enum_type.parquet contains 1 column (ENUM) with 3 rows.
+  const std::string sample(getExampleFilePath("v2_page.parquet"));
+
+  facebook::velox::dwio::common::ReaderOptions readerOptions{leafPool_.get()};
+  auto reader = createReader(sample, readerOptions);
+  EXPECT_EQ(reader->numberOfRows(), 5ULL);
+
+  auto rowType = reader->typeWithId();
+  EXPECT_EQ(rowType->type()->kind(), TypeKind::ROW);
+  EXPECT_EQ(rowType->size(), 1ULL);
+
+  EXPECT_EQ(rowType->childAt(0)->type()->kind(), TypeKind::BIGINT);
+
+  auto outputRowType = ROW({"regionkey"}, {BIGINT()});
+  auto rowReaderOpts = getReaderOpts(outputRowType);
+  rowReaderOpts.setScanSpec(makeScanSpec(outputRowType));
+  auto rowReader = reader->createRowReader(rowReaderOpts);
+
+  auto expected = makeRowVector({makeFlatVector<int64_t>({0, 1, 2, 3, 4})});
+
+  assertReadWithReaderAndExpected(
+      outputRowType, *rowReader, expected, *leafPool_);
+}