fix: configurable fallback when parquet vectorized reader is disabled (#4352)

common/src/main/scala/org/apache/comet/CometConf.scala

@@ -783,6 +783,19 @@ object CometConf extends ShimCometConf {
       .booleanConf
       .createWithDefault(true)
 
+  val COMET_SCAN_ALLOW_DISABLED_PARQUET_VECTORIZED_READER: ConfigEntry[Boolean] =
+    conf("spark.comet.scan.allowDisabledParquetVectorizedReader")
+      .category(CATEGORY_SCAN)
+      .doc(
+        "Whether to allow Comet's native scan to replace the Parquet scan when Spark's " +
+          s"${SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key} is set to false. By default " +
+          "(false), Comet falls back to Spark in that case, because Comet's native readers " +
+          "mirror Spark's vectorized reader semantics rather than Spark's parquet-mr " +
+          "(non-vectorized) semantics, which permit silent overflow / null-on-narrowing " +
+          s"that Comet has no equivalent for. $COMPAT_GUIDE.")
+      .booleanConf
+      .createWithDefault(false)
+
   val COMET_EXEC_STRICT_FLOATING_POINT: ConfigEntry[Boolean] =
     conf("spark.comet.exec.strictFloatingPoint")
       .category(CATEGORY_EXEC)

dev/diffs/4.0.2.diff

@@ -2877,18 +2877,9 @@ index 0acb21f3e6f..e7c65429119 100644
        val e = testSchemaMismatch(dir.getCanonicalPath, vectorizedReaderEnabled = true)
        assert(e.getCause.isInstanceOf[SchemaColumnConvertNotSupportedException])
 diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala
-index 09ed6955a51..82924c83eb5 100644
+index 09ed6955a51..236a4e99824 100644
 --- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala
 +++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala
-@@ -24,7 +24,7 @@ import org.apache.parquet.format.converter.ParquetMetadataConverter
- import org.apache.parquet.hadoop.{ParquetFileReader, ParquetOutputFormat}
-
- import org.apache.spark.SparkException
--import org.apache.spark.sql.{DataFrame, QueryTest, Row}
-+import org.apache.spark.sql.{DataFrame, IgnoreCometNativeDataFusion, QueryTest, Row}
- import org.apache.spark.sql.execution.adaptive.AdaptiveSparkPlanHelper
- import org.apache.spark.sql.execution.datasources.SchemaColumnConvertNotSupportedException
- import org.apache.spark.sql.functions.col
 @@ -65,7 +65,9 @@ class ParquetTypeWideningSuite
      withClue(
        s"with dictionary encoding '$dictionaryEnabled' with timestamp rebase mode " +
@@ -2919,66 +2910,6 @@ index 09ed6955a51..82924c83eb5 100644
      )
    }
    test(s"parquet widening conversion $fromType -> $toType") {
-@@ -231,7 +234,8 @@ class ParquetTypeWideningSuite
-       (Seq("2020-01-01", "2020-01-02", "1312-02-27"), DateType, TimestampType)
-     )
-   }
--  test(s"unsupported parquet conversion $fromType -> $toType") {
-+  test(s"unsupported parquet conversion $fromType -> $toType",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     checkAllParquetReaders(values, fromType, toType, expectError = true)
-   }
-
-@@ -257,7 +261,8 @@ class ParquetTypeWideningSuite
-       (Seq("1", "2"), LongType, DecimalType(LongDecimal.precision, 1))
-     )
-   }
--  test(s"unsupported parquet conversion $fromType -> $toType") {
-+  test(s"unsupported parquet conversion $fromType -> $toType",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     checkAllParquetReaders(values, fromType, toType,
-       expectError =
-       // parquet-mr allows reading decimals into a smaller precision decimal type without
-@@ -271,7 +276,8 @@ class ParquetTypeWideningSuite
-       (Seq("2020-01-01", "2020-01-02", "1312-02-27"), TimestampNTZType, DateType))
-     outputTimestampType <- ParquetOutputTimestampType.values
-   }
--  test(s"unsupported parquet timestamp conversion $fromType ($outputTimestampType) -> $toType") {
-+  test(s"unsupported parquet timestamp conversion $fromType ($outputTimestampType) -> $toType",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     withSQLConf(
-       SQLConf.PARQUET_OUTPUT_TIMESTAMP_TYPE.key -> outputTimestampType.toString,
-       SQLConf.PARQUET_INT96_REBASE_MODE_IN_WRITE.key -> LegacyBehaviorPolicy.CORRECTED.toString
-@@ -291,7 +297,8 @@ class ParquetTypeWideningSuite
-       Seq(7 -> 5, 10 -> 5, 20 -> 5, 12 -> 10, 20 -> 10, 22 -> 20)
-   }
-   test(
--    s"parquet decimal precision change Decimal($fromPrecision, 2) -> Decimal($toPrecision, 2)") {
-+    s"parquet decimal precision change Decimal($fromPrecision, 2) -> Decimal($toPrecision, 2)",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     checkAllParquetReaders(
-       values = Seq("1.23", "10.34"),
-       fromType = DecimalType(fromPrecision, 2),
-@@ -322,7 +329,8 @@ class ParquetTypeWideningSuite
-       Seq((5, 2) -> (6, 4), (10, 4) -> (12, 7), (20, 5) -> (22, 8))
-   }
-   test(s"parquet decimal precision and scale change Decimal($fromPrecision, $fromScale) -> " +
--    s"Decimal($toPrecision, $toScale)"
-+    s"Decimal($toPrecision, $toScale)",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")
-   ) {
-     checkAllParquetReaders(
-       values = Seq("1.23", "10.34"),
-@@ -336,7 +344,8 @@ class ParquetTypeWideningSuite
-     )
-   }
-
--  test("parquet decimal type change Decimal(5, 2) -> Decimal(3, 2) overflows with parquet-mr") {
-+  test("parquet decimal type change Decimal(5, 2) -> Decimal(3, 2) overflows with parquet-mr",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     withTempDir { dir =>
-       withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false") {
-         writeParquetFiles(
 diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/debug/DebuggingSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/debug/DebuggingSuite.scala
 index b8f3ea3c6f3..bbd44221288 100644
 --- a/sql/core/src/test/scala/org/apache/spark/sql/execution/debug/DebuggingSuite.scala

dev/diffs/4.1.1.diff

@@ -3036,18 +3036,9 @@ index 56076175d60..5872d9962cc 100644
        val e = testSchemaMismatch(dir.getCanonicalPath, vectorizedReaderEnabled = true)
        assert(e.getCause.isInstanceOf[SchemaColumnConvertNotSupportedException])
 diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala
-index 09ed6955a51..82924c83eb5 100644
+index 09ed6955a51..236a4e99824 100644
 --- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala
 +++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetTypeWideningSuite.scala
-@@ -24,7 +24,7 @@ import org.apache.parquet.format.converter.ParquetMetadataConverter
- import org.apache.parquet.hadoop.{ParquetFileReader, ParquetOutputFormat}
-
- import org.apache.spark.SparkException
--import org.apache.spark.sql.{DataFrame, QueryTest, Row}
-+import org.apache.spark.sql.{DataFrame, IgnoreCometNativeDataFusion, QueryTest, Row}
- import org.apache.spark.sql.execution.adaptive.AdaptiveSparkPlanHelper
- import org.apache.spark.sql.execution.datasources.SchemaColumnConvertNotSupportedException
- import org.apache.spark.sql.functions.col
 @@ -65,7 +65,9 @@ class ParquetTypeWideningSuite
      withClue(
        s"with dictionary encoding '$dictionaryEnabled' with timestamp rebase mode " +
@@ -3078,66 +3069,6 @@ index 09ed6955a51..82924c83eb5 100644
      )
    }
    test(s"parquet widening conversion $fromType -> $toType") {
-@@ -231,7 +234,8 @@ class ParquetTypeWideningSuite
-       (Seq("2020-01-01", "2020-01-02", "1312-02-27"), DateType, TimestampType)
-     )
-   }
--  test(s"unsupported parquet conversion $fromType -> $toType") {
-+  test(s"unsupported parquet conversion $fromType -> $toType",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     checkAllParquetReaders(values, fromType, toType, expectError = true)
-   }
-
-@@ -257,7 +261,8 @@ class ParquetTypeWideningSuite
-       (Seq("1", "2"), LongType, DecimalType(LongDecimal.precision, 1))
-     )
-   }
--  test(s"unsupported parquet conversion $fromType -> $toType") {
-+  test(s"unsupported parquet conversion $fromType -> $toType",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     checkAllParquetReaders(values, fromType, toType,
-       expectError =
-       // parquet-mr allows reading decimals into a smaller precision decimal type without
-@@ -271,7 +276,8 @@ class ParquetTypeWideningSuite
-       (Seq("2020-01-01", "2020-01-02", "1312-02-27"), TimestampNTZType, DateType))
-     outputTimestampType <- ParquetOutputTimestampType.values
-   }
--  test(s"unsupported parquet timestamp conversion $fromType ($outputTimestampType) -> $toType") {
-+  test(s"unsupported parquet timestamp conversion $fromType ($outputTimestampType) -> $toType",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     withSQLConf(
-       SQLConf.PARQUET_OUTPUT_TIMESTAMP_TYPE.key -> outputTimestampType.toString,
-       SQLConf.PARQUET_INT96_REBASE_MODE_IN_WRITE.key -> LegacyBehaviorPolicy.CORRECTED.toString
-@@ -291,7 +297,8 @@ class ParquetTypeWideningSuite
-       Seq(7 -> 5, 10 -> 5, 20 -> 5, 12 -> 10, 20 -> 10, 22 -> 20)
-   }
-   test(
--    s"parquet decimal precision change Decimal($fromPrecision, 2) -> Decimal($toPrecision, 2)") {
-+    s"parquet decimal precision change Decimal($fromPrecision, 2) -> Decimal($toPrecision, 2)",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     checkAllParquetReaders(
-       values = Seq("1.23", "10.34"),
-       fromType = DecimalType(fromPrecision, 2),
-@@ -322,7 +329,8 @@ class ParquetTypeWideningSuite
-       Seq((5, 2) -> (6, 4), (10, 4) -> (12, 7), (20, 5) -> (22, 8))
-   }
-   test(s"parquet decimal precision and scale change Decimal($fromPrecision, $fromScale) -> " +
--    s"Decimal($toPrecision, $toScale)"
-+    s"Decimal($toPrecision, $toScale)",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")
-   ) {
-     checkAllParquetReaders(
-       values = Seq("1.23", "10.34"),
-@@ -336,7 +344,8 @@ class ParquetTypeWideningSuite
-     )
-   }
-
--  test("parquet decimal type change Decimal(5, 2) -> Decimal(3, 2) overflows with parquet-mr") {
-+  test("parquet decimal type change Decimal(5, 2) -> Decimal(3, 2) overflows with parquet-mr",
-+    IgnoreCometNativeDataFusion("https://github.com/apache/datafusion-comet/issues/4352")) {
-     withTempDir { dir =>
-       withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false") {
-         writeParquetFiles(
 diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetVariantShreddingSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetVariantShreddingSuite.scala
 index 1cc6d3afbee..8275727fbb4 100644
 --- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetVariantShreddingSuite.scala

docs/source/user-guide/latest/compatibility/scans.md

@@ -79,6 +79,12 @@ requires `spark.comet.exec.enabled=true` because the scan node must be wrapped b
 - Duplicate field names in case-insensitive mode (e.g., a Parquet file with both `B` and `b` columns)
   are detected at read time and raise a `SparkRuntimeException` with error class `_LEGACY_ERROR_TEMP_2093`,
   matching Spark's behavior.
+- `spark.sql.parquet.enableVectorizedReader=false`. Disabling the vectorized reader opts into
+  Spark's parquet-mr semantics (silent overflow, null-on-narrowing), which Comet's native reader
+  does not replicate. By default Comet falls back to Spark in this case. Set
+  `spark.comet.scan.allowDisabledParquetVectorizedReader=true` to opt in to running the
+  `native_datafusion` scan regardless. See
+  [#4352](https://github.com/apache/datafusion-comet/issues/4352).
 
 The following `native_datafusion` limitations may produce incorrect results on Spark versions prior to 4.0
 without falling back to Spark:

spark/src/main/scala/org/apache/comet/rules/CometScanRule.scala

@@ -207,6 +207,19 @@ case class CometScanRule(session: SparkSession)
         s"$SCAN_NATIVE_DATAFUSION scan requires ${COMET_EXEC_ENABLED.key} to be enabled")
       return None
     }
+    // Disabling the vectorized reader opts into parquet-mr's permissive behavior
+    // (silent overflow / null-on-narrowing). Comet has no parquet-mr-equivalent
+    // backend, so by default fall back to Spark. Users can opt in to letting Comet
+    // replace the scan via COMET_SCAN_ALLOW_DISABLED_PARQUET_VECTORIZED_READER.
+    if (!conf.parquetVectorizedReaderEnabled &&
+      !COMET_SCAN_ALLOW_DISABLED_PARQUET_VECTORIZED_READER.get()) {
+      withInfo(
+        scanExec,
+        s"$SCAN_NATIVE_DATAFUSION scan is incompatible with " +
+          s"${SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key}=false; set " +
+          s"${COMET_SCAN_ALLOW_DISABLED_PARQUET_VECTORIZED_READER.key}=true to opt in")
+      return None
+    }
     if (!CometNativeScan.isSupported(scanExec)) {
       return None
     }

spark/src/test/scala/org/apache/spark/sql/CometTestBase.scala

@@ -86,6 +86,7 @@ abstract class CometTestBase
     conf.set(CometConf.COMET_SPARK_TO_ARROW_ENABLED.key, "true")
     conf.set(CometConf.COMET_NATIVE_SCAN_ENABLED.key, "true")
     conf.set(CometConf.COMET_PARQUET_UNSIGNED_SMALL_INT_CHECK.key, "false")
+    conf.set(CometConf.COMET_SCAN_ALLOW_DISABLED_PARQUET_VECTORIZED_READER.key, "true")
     conf.set(CometConf.COMET_ONHEAP_MEMORY_OVERHEAD.key, "2g")
     conf.set(CometConf.COMET_EXEC_SORT_MERGE_JOIN_WITH_JOIN_FILTER_ENABLED.key, "true")
     // SortOrder is incompatible for mixed zero and negative zero floating point values, but