[SPARK-55716][SQL] Fix V1 file source NOT NULL constraint enforcement

V1 file-based DataSource writes (parquet/orc/json) silently accept null values into NOT NULL columns. The root cause:

1. `DataSource.resolveRelation()` calls `dataSchema.asNullable` (SPARK-13738) for read safety, stripping NOT NULL recursively.
2. `CreateDataSourceTableCommand` stores this all-nullable schema in the catalog, permanently losing NOT NULL info.
3. `PreprocessTableInsertion` never injects `AssertNotNull` because the schema is all-nullable.

Fix:
- `CreateDataSourceTableCommand`: preserve user-specified nullability via recursive merging into the resolved schema.
- `PreprocessTableInsertion`: restore nullability flags from catalog schema before null checks.
- Add legacy config `spark.sql.legacy.allowNullInsertForFileSourceTables` (default false) for backward compatibility.

Covers top-level and nested types (array elements, struct fields, map values).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: yaooqinn

docs/sql-migration-guide.md

@@ -25,6 +25,7 @@ license: |
 ## Upgrading from Spark SQL 4.1 to 4.2
 
 - Since Spark 4.2, Spark enables order-independent checksums for shuffle outputs by default to detect data inconsistencies during indeterminate shuffle stage retries. If a checksum mismatch is detected, Spark rolls back and re-executes all succeeding stages that depend on the shuffle output. If rolling back is not possible for some succeeding stages, the job will fail. To restore the previous behavior, set `spark.sql.shuffle.orderIndependentChecksum.enabled` and `spark.sql.shuffle.orderIndependentChecksum.enableFullRetryOnMismatch` to `false`.
+- Since Spark 4.2, Spark can enforce NOT NULL constraints when inserting into V1 file-based data source tables (e.g., Parquet, ORC, JSON) by setting `spark.sql.legacy.allowNullInsertForFileSourceTables` to `false`. Previously (and still by default), null values are silently accepted into NOT NULL columns.
 - Since Spark 4.2, support for Derby JDBC datasource is deprecated.
 
 ## Upgrading from Spark SQL 4.0 to 4.1

sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -4743,6 +4743,17 @@ object SQLConf {
       .enumConf(StoreAssignmentPolicy)
       .createWithDefault(StoreAssignmentPolicy.ANSI)
 
+  val LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT =
+    buildConf("spark.sql.legacy.allowNullInsertForFileSourceTables")
+      .internal()
+      .doc("When true (default, legacy behavior), Spark does not enforce NOT NULL constraints " +
+        "when inserting data into file-based data source tables (e.g., Parquet, ORC, JSON). " +
+        "When false, Spark properly enforces NOT NULL constraints for file-based tables, " +
+        "consistent with the behavior for other data sources and V2 catalog tables.")
+      .version("4.2.0")
+      .booleanConf
+      .createWithDefault(true)
+
   val ANSI_ENABLED = buildConf(SqlApiConfHelper.ANSI_ENABLED_KEY)
     .doc("When true, Spark SQL uses an ANSI compliant dialect instead of being Hive compliant. " +
       "For example, Spark will throw an exception at runtime instead of returning null results " +

sql/core/src/main/scala/org/apache/spark/sql/execution/command/createDataSourceTables.scala

@@ -29,7 +29,7 @@ import org.apache.spark.sql.errors.QueryCompilationErrors
 import org.apache.spark.sql.execution.CommandExecutionMode
 import org.apache.spark.sql.execution.datasources._
 import org.apache.spark.sql.sources.BaseRelation
-import org.apache.spark.sql.types.StructType
+import org.apache.spark.sql.types.{ArrayType, DataType, MapType, StructType}
 import org.apache.spark.util.ArrayImplicits._
 
 /**
@@ -107,8 +107,17 @@ case class CreateDataSourceTableCommand(table: CatalogTable, ignoreIfExists: Boo
         table.copy(schema = new StructType(), partitionColumnNames = Nil)
 
       case _ =>
+        // Merge nullability from the user-specified schema into the resolved schema.
+        // DataSource.resolveRelation() calls dataSchema.asNullable which strips NOT NULL
+        // constraints. We restore nullability from the original user schema while keeping
+        // the resolved data types (which may include CharVarchar normalization, metadata, etc.)
+        val resolvedSchema = if (table.schema.nonEmpty) {
+          restoreNullability(dataSource.schema, table.schema)
+        } else {
+          dataSource.schema
+        }
         table.copy(
-          schema = dataSource.schema,
+          schema = resolvedSchema,
           partitionColumnNames = partitionColumnNames,
           // If metastore partition management for file source tables is enabled, we start off with
           // partition provider hive, but no partitions in the metastore. The user has to call
@@ -122,6 +131,39 @@ case class CreateDataSourceTableCommand(table: CatalogTable, ignoreIfExists: Boo
 
     Seq.empty[Row]
   }
+
+  /**
+   * Recursively restores nullability from the original user-specified schema into
+   * the resolved schema. The resolved schema's data types are preserved (they may
+   * contain CharVarchar normalization, metadata, etc.), but nullability flags
+   * (top-level and nested) are taken from the original schema.
+   */
+  private def restoreNullability(resolved: StructType, original: StructType): StructType = {
+    val originalFields = original.fields.map(f => f.name -> f).toMap
+    StructType(resolved.fields.map { resolvedField =>
+      originalFields.get(resolvedField.name) match {
+        case Some(origField) =>
+          resolvedField.copy(
+            nullable = origField.nullable,
+            dataType = restoreDataTypeNullability(resolvedField.dataType, origField.dataType))
+        case None => resolvedField
+      }
+    })
+  }
+
+  private def restoreDataTypeNullability(resolved: DataType, original: DataType): DataType = {
+    (resolved, original) match {
+      case (r: StructType, o: StructType) => restoreNullability(r, o)
+      case (ArrayType(rElem, _), ArrayType(oElem, oNull)) =>
+        ArrayType(restoreDataTypeNullability(rElem, oElem), oNull)
+      case (MapType(rKey, rVal, _), MapType(oKey, oVal, oValNull)) =>
+        MapType(
+          restoreDataTypeNullability(rKey, oKey),
+          restoreDataTypeNullability(rVal, oVal),
+          oValNull)
+      case _ => resolved
+    }
+  }
 }
 
 /**

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/rules.scala

@@ -39,7 +39,7 @@ import org.apache.spark.sql.execution.datasources.{CreateTable => CreateTableV1}
 import org.apache.spark.sql.execution.datasources.v2.FileDataSourceV2
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.sources.InsertableRelation
-import org.apache.spark.sql.types.{MetadataBuilder, StructField, StructType}
+import org.apache.spark.sql.types.{ArrayType, DataType, MapType, MetadataBuilder, StructField, StructType}
 import org.apache.spark.sql.util.PartitioningUtils.normalizePartitionSpec
 import org.apache.spark.sql.util.SchemaUtils
 import org.apache.spark.util.ArrayImplicits._
@@ -470,7 +470,29 @@ object PreprocessTableInsertion extends ResolveInsertionBase {
       insert.partitionSpec, partColNames, tblName, conf.resolver)
 
     val staticPartCols = normalizedPartSpec.filter(_._2.isDefined).keySet
-    val expectedColumns = insert.table.output.filterNot(a => staticPartCols.contains(a.name))
+    val expectedColumns = {
+      val cols = insert.table.output.filterNot(a => staticPartCols.contains(a.name))
+      // When the legacy config is disabled, restore the original nullability from the
+      // catalog table schema. HadoopFsRelation forces dataSchema.asNullable for safe reads,
+      // which strips NOT NULL constraints (both top-level and nested) from the
+      // LogicalRelation output. We restore nullability so that AssertNotNull checks are
+      // properly injected.
+      if (!conf.getConf(SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT)) {
+        catalogTable.map { ct =>
+          val catalogFields = ct.schema.fields.map(f => f.name -> f).toMap
+          cols.map { col =>
+            catalogFields.get(col.name) match {
+              case Some(field) =>
+                col.withNullability(field.nullable)
+                  .withDataType(restoreDataTypeNullability(col.dataType, field.dataType))
+              case None => col
+            }
+          }
+        }.getOrElse(cols)
+      } else {
+        cols
+      }
+    }
 
     val partitionsTrackedByCatalog = catalogTable.isDefined &&
       catalogTable.get.partitionColumnNames.nonEmpty &&
@@ -546,6 +568,34 @@ object PreprocessTableInsertion extends ResolveInsertionBase {
         case _ => i
       }
   }
+
+  /**
+   * Recursively restores nullability flags from the original data type into the resolved
+   * data type, keeping the resolved type structure intact.
+   */
+  private def restoreDataTypeNullability(resolved: DataType, original: DataType): DataType = {
+    (resolved, original) match {
+      case (r: StructType, o: StructType) =>
+        val origFields = o.fields.map(f => f.name -> f).toMap
+        StructType(r.fields.map { rf =>
+          origFields.get(rf.name) match {
+            case Some(of) =>
+              rf.copy(
+                nullable = of.nullable,
+                dataType = restoreDataTypeNullability(rf.dataType, of.dataType))
+            case None => rf
+          }
+        })
+      case (ArrayType(rElem, _), ArrayType(oElem, oNull)) =>
+        ArrayType(restoreDataTypeNullability(rElem, oElem), oNull)
+      case (MapType(rKey, rVal, _), MapType(oKey, oVal, oValNull)) =>
+        MapType(
+          restoreDataTypeNullability(rKey, oKey),
+          restoreDataTypeNullability(rVal, oVal),
+          oValNull)
+      case _ => resolved
+    }
+  }
 }
 
 /**

sql/core/src/test/scala/org/apache/spark/sql/execution/command/v1/ShowCreateTableSuite.scala

@@ -185,7 +185,7 @@ trait ShowCreateTableSuiteBase extends command.ShowCreateTableSuiteBase
       val showDDL = getShowCreateDDL(t)
       assert(showDDL === Array(
         s"CREATE TABLE $fullName (",
-        "a BIGINT,",
+        "a BIGINT NOT NULL,",
         "b BIGINT DEFAULT 42,",
         "c STRING COLLATE UTF8_BINARY DEFAULT 'abc, \"def\"' COMMENT 'comment')",
         "USING parquet",

sql/core/src/test/scala/org/apache/spark/sql/sources/InsertSuite.scala

@@ -2851,6 +2851,188 @@ class InsertSuite extends DataSourceTest with SharedSparkSession {
     }
   }
 
+  test("SPARK-55716: V1 INSERT rejects null into NOT NULL column for file sources") {
+    Seq("parquet", "orc", "json").foreach { format =>
+      withSQLConf(SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "false") {
+        withTable("t") {
+          sql(s"CREATE TABLE t(i INT NOT NULL, s STRING NOT NULL) USING $format")
+          // V1 DataSource writes now enforce NOT NULL constraints via AssertNotNull
+          val e1 = intercept[SparkRuntimeException] {
+            sql("INSERT INTO t VALUES(null, 'a')")
+          }
+          assert(e1.getCondition === "NOT_NULL_ASSERT_VIOLATION")
+          val e2 = intercept[SparkRuntimeException] {
+            sql("INSERT INTO t VALUES(1, null)")
+          }
+          assert(e2.getCondition === "NOT_NULL_ASSERT_VIOLATION")
+          // Valid insert should succeed
+          sql("INSERT INTO t VALUES(1, 'a')")
+          checkAnswer(spark.table("t"), Seq(Row(1, "a")))
+        }
+      }
+    }
+  }
+
+  test("SPARK-55716: V1 INSERT NOT NULL enforcement respects storeAssignmentPolicy") {
+    Seq("parquet", "orc").foreach { format =>
+      // ANSI mode (default): rejects null
+      withSQLConf(
+        SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "false",
+        SQLConf.STORE_ASSIGNMENT_POLICY.key -> SQLConf.StoreAssignmentPolicy.ANSI.toString) {
+        withTable("t") {
+          sql(s"CREATE TABLE t(i INT NOT NULL) USING $format")
+          val e = intercept[SparkRuntimeException] {
+            sql("INSERT INTO t VALUES(null)")
+          }
+          assert(e.getCondition === "NOT_NULL_ASSERT_VIOLATION")
+        }
+      }
+      // STRICT mode: also rejects null (fails at analysis with type mismatch)
+      withSQLConf(
+        SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "false",
+        SQLConf.STORE_ASSIGNMENT_POLICY.key -> SQLConf.StoreAssignmentPolicy.STRICT.toString) {
+        withTable("t") {
+          sql(s"CREATE TABLE t(i INT NOT NULL) USING $format")
+          intercept[AnalysisException] {
+            sql("INSERT INTO t VALUES(null)")
+          }
+        }
+      }
+      // LEGACY mode: allows null (no AssertNotNull injected)
+      withSQLConf(
+        SQLConf.STORE_ASSIGNMENT_POLICY.key -> SQLConf.StoreAssignmentPolicy.LEGACY.toString) {
+        withTable("t") {
+          sql(s"CREATE TABLE t(i INT NOT NULL) USING $format")
+          sql("INSERT INTO t VALUES(null)")
+          checkAnswer(spark.table("t"), Seq(Row(null)))
+        }
+      }
+      // Legacy config: allows null even in ANSI mode
+      withSQLConf(
+        SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "true") {
+        withTable("t") {
+          sql(s"CREATE TABLE t(i INT NOT NULL) USING $format")
+          sql("INSERT INTO t VALUES(null)")
+          checkAnswer(spark.table("t"), Seq(Row(null)))
+        }
+      }
+    }
+  }
+
+  test("SPARK-55716: V1 INSERT rejects null with V2 file source path") {
+    Seq("parquet", "orc").foreach { format =>
+      withSQLConf(
+        SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "false",
+        SQLConf.USE_V1_SOURCE_LIST.key -> "") {
+        withTable("t") {
+          sql(s"CREATE TABLE t(i INT NOT NULL, s STRING NOT NULL) USING $format")
+          val e = intercept[SparkRuntimeException] {
+            sql("INSERT INTO t VALUES(null, 'a')")
+          }
+          assert(e.getCondition === "NOT_NULL_ASSERT_VIOLATION")
+        }
+      }
+    }
+  }
+
+  test("SPARK-55716: V1 INSERT rejects null array element for NOT NULL element type") {
+    Seq("parquet", "orc").foreach { format =>
+      withSQLConf(SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "false") {
+      withTable("t") {
+        val schema = new StructType()
+          .add("a", ArrayType(IntegerType, containsNull = false))
+        spark.sessionState.catalog.createTable(
+          CatalogTable(
+            identifier = TableIdentifier("t"),
+            tableType = CatalogTableType.MANAGED,
+            storage = CatalogStorageFormat.empty,
+            schema = schema,
+            provider = Some(format)),
+          ignoreIfExists = false)
+        val e = intercept[SparkRuntimeException] {
+          sql("INSERT INTO t SELECT array(1, null, 3)")
+        }
+        assert(e.getCondition === "NOT_NULL_ASSERT_VIOLATION")
+        // Valid insert should succeed
+        sql("INSERT INTO t SELECT array(1, 2, 3)")
+        checkAnswer(spark.table("t"), Seq(Row(Seq(1, 2, 3))))
+      }
+      }
+    }
+  }
+
+  test("SPARK-55716: V1 INSERT rejects null struct field for NOT NULL field") {
+    Seq("parquet", "orc").foreach { format =>
+      withSQLConf(SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "false") {
+      withTable("t") {
+        val schema = new StructType()
+          .add("s", new StructType()
+            .add("x", IntegerType, nullable = false)
+            .add("y", StringType, nullable = false))
+        spark.sessionState.catalog.createTable(
+          CatalogTable(
+            identifier = TableIdentifier("t"),
+            tableType = CatalogTableType.MANAGED,
+            storage = CatalogStorageFormat.empty,
+            schema = schema,
+            provider = Some(format)),
+          ignoreIfExists = false)
+        val e = intercept[SparkRuntimeException] {
+          sql("INSERT INTO t SELECT named_struct('x', null, 'y', 'hello')")
+        }
+        assert(e.getCondition === "NOT_NULL_ASSERT_VIOLATION")
+        // Valid insert should succeed
+        sql("INSERT INTO t SELECT named_struct('x', 1, 'y', 'hello')")
+        checkAnswer(spark.table("t"), Seq(Row(Row(1, "hello"))))
+      }
+      }
+    }
+  }
+
+  test("SPARK-55716: V1 INSERT rejects null map value for NOT NULL value type") {
+    Seq("parquet", "orc").foreach { format =>
+      withSQLConf(SQLConf.LEGACY_NO_NULL_CHECK_FOR_FILE_SOURCE_INSERT.key -> "false") {
+      withTable("t") {
+        val schema = new StructType()
+          .add("m", MapType(StringType, IntegerType, valueContainsNull = false))
+        spark.sessionState.catalog.createTable(
+          CatalogTable(
+            identifier = TableIdentifier("t"),
+            tableType = CatalogTableType.MANAGED,
+            storage = CatalogStorageFormat.empty,
+            schema = schema,
+            provider = Some(format)),
+          ignoreIfExists = false)
+        val e = intercept[SparkRuntimeException] {
+          sql("INSERT INTO t SELECT map('a', 1, 'b', null)")
+        }
+        assert(e.getCondition === "NOT_NULL_ASSERT_VIOLATION")
+        // Valid insert should succeed
+        sql("INSERT INTO t SELECT map('a', 1, 'b', 2)")
+        checkAnswer(spark.table("t"), Seq(Row(Map("a" -> 1, "b" -> 2))))
+      }
+      }
+    }
+  }
+
+  test("SPARK-55716: V1 DataFrame write ignores NOT NULL schema constraint") {
+    Seq("parquet", "orc").foreach { format =>
+      withTempPath { path =>
+        val data = Seq(Row(null, "hello", 1.0), Row(1, null, 2.0), Row(2, "world", null))
+        val df = spark.createDataFrame(
+          spark.sparkContext.parallelize(data),
+          new StructType()
+            .add("id", IntegerType, nullable = true)
+            .add("name", StringType, nullable = true)
+            .add("value", DoubleType, nullable = true))
+        // V1 DataSource writes do not enforce NOT NULL constraints
+        df.write.mode(SaveMode.Overwrite).format(format).save(path.getCanonicalPath)
+        val result = spark.read.format(format).load(path.getCanonicalPath)
+        checkAnswer(result, data)
+      }
+    }
+  }
+
   test("UNSUPPORTED_OVERWRITE.PATH: Can't overwrite a path that is also being read from") {
     val tableName = "t1"
     withTable(tableName) {

sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkGetColumnsOperation.scala

@@ -224,7 +224,7 @@ private[hive] class SparkGetColumnsOperation(
           null, // SQL_DATETIME_SUB
           null, // CHAR_OCTET_LENGTH
           ordinal.asInstanceOf[AnyRef], // ORDINAL_POSITION, 1-based
-          "YES", // IS_NULLABLE
+          (if (column.nullable) "YES" else "NO"), // IS_NULLABLE
           null, // SCOPE_CATALOG
           null, // SCOPE_SCHEMA
           null, // SCOPE_TABLE