Reject reader timestamp types without a second-based unit

cpp/include/cudf/io/orc.hpp

@@ -277,9 +277,26 @@ class orc_reader_options {
   /**
    * @brief Sets timestamp type to which timestamp column will be cast.
    *
+   * Only TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS, TIMESTAMP_MICROSECONDS and
+   * TIMESTAMP_NANOSECONDS are supported as the target type; EMPTY, the default, reads timestamps
+   * as TIMESTAMP_NANOSECONDS. For a coarser resolution such as TIMESTAMP_DAYS, cast the output
+   * column instead.
+   *
    * @param type Type of timestamp
+   *
+   * @throw cudf::logic_error if `type` is not EMPTY, TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS,
+   * TIMESTAMP_MICROSECONDS or TIMESTAMP_NANOSECONDS
    */
-  void set_timestamp_type(data_type type) { _timestamp_type = type; }
+  void set_timestamp_type(data_type type)
+  {
+    CUDF_EXPECTS(type.id() == type_id::EMPTY or type.id() == type_id::TIMESTAMP_SECONDS or
+                   type.id() == type_id::TIMESTAMP_MILLISECONDS or
+                   type.id() == type_id::TIMESTAMP_MICROSECONDS or
+                   type.id() == type_id::TIMESTAMP_NANOSECONDS,
+                 "timestamp_type must be EMPTY, TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS, "
+                 "TIMESTAMP_MICROSECONDS or TIMESTAMP_NANOSECONDS");
+    _timestamp_type = type;
+  }
 
   /**
    * @brief Set columns that should be read as 128-bit Decimal
@@ -405,6 +422,9 @@ class orc_reader_options_builder {
    *
    * @param type Type of timestamp
    * @return this for chaining
+   *
+   * @throw cudf::logic_error if `type` is not EMPTY, TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS,
+   * TIMESTAMP_MICROSECONDS or TIMESTAMP_NANOSECONDS
    */
   orc_reader_options_builder& timestamp_type(data_type type)
   {

cpp/include/cudf/io/parquet.hpp

@@ -619,9 +619,26 @@ class parquet_reader_options {
   /**
    * @brief Sets timestamp_type used to cast timestamp columns.
    *
+   * Only TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS, TIMESTAMP_MICROSECONDS and
+   * TIMESTAMP_NANOSECONDS are supported as the target type; EMPTY, the default, keeps each
+   * column's own resolution. For a coarser resolution such as TIMESTAMP_DAYS, cast the output
+   * column instead.
+   *
+   * @throws cudf::logic_error if `type` is not EMPTY, TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS,
+   * TIMESTAMP_MICROSECONDS or TIMESTAMP_NANOSECONDS
+   *
    * @param type The timestamp data_type to which all timestamp columns need to be cast
    */
-  void set_timestamp_type(data_type type) { _timestamp_type = type; }
+  void set_timestamp_type(data_type type)
+  {
+    CUDF_EXPECTS(type.id() == type_id::EMPTY or type.id() == type_id::TIMESTAMP_SECONDS or
+                   type.id() == type_id::TIMESTAMP_MILLISECONDS or
+                   type.id() == type_id::TIMESTAMP_MICROSECONDS or
+                   type.id() == type_id::TIMESTAMP_NANOSECONDS,
+                 "timestamp_type must be EMPTY, TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS, "
+                 "TIMESTAMP_MICROSECONDS or TIMESTAMP_NANOSECONDS");
+    _timestamp_type = type;
+  }
 
   /**
    * @brief Sets decimal width used to cast decimal columns.
@@ -900,6 +917,9 @@ class parquet_reader_options_builder {
   /**
    * @brief timestamp_type used to cast timestamp columns.
    *
+   * @throws cudf::logic_error if `type` is not EMPTY, TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS,
+   * TIMESTAMP_MICROSECONDS or TIMESTAMP_NANOSECONDS
+   *
    * @param type The timestamp data_type to which all timestamp columns need to be cast
    * @return this for chaining
    */

cpp/tests/io/orc_test.cpp

@@ -1539,6 +1539,31 @@ TEST_F(OrcReaderTest, ZeroColumnsPreservesRowCount)
   EXPECT_EQ(result.tbl->view().num_rows(), num_rows);
 }
 
+TEST_F(OrcReaderTest, TimestampTypeMustHaveSecondBasedUnit)
+{
+  // The decode kernel converts timestamps to seconds, milliseconds, microseconds or nanoseconds
+  // and stores 64-bit values, so a request for TIMESTAMP_DAYS would write 8-byte nanosecond
+  // counts into a column allocated at 4 bytes per row.
+  auto options = cudf::io::orc_reader_options{};
+  for (auto const id : {cudf::type_id::EMPTY,
+                        cudf::type_id::TIMESTAMP_SECONDS,
+                        cudf::type_id::TIMESTAMP_MILLISECONDS,
+                        cudf::type_id::TIMESTAMP_MICROSECONDS,
+                        cudf::type_id::TIMESTAMP_NANOSECONDS}) {
+    EXPECT_NO_THROW(options.set_timestamp_type(cudf::data_type{id}));
+    EXPECT_EQ(options.get_timestamp_type().id(), id);
+  }
+  for (auto const id :
+       {cudf::type_id::TIMESTAMP_DAYS, cudf::type_id::DURATION_SECONDS, cudf::type_id::INT64}) {
+    EXPECT_THROW(options.set_timestamp_type(cudf::data_type{id}), cudf::logic_error);
+  }
+  // A rejected type leaves the previous one in place.
+  EXPECT_EQ(options.get_timestamp_type().id(), cudf::type_id::TIMESTAMP_NANOSECONDS);
+  EXPECT_THROW(cudf::io::orc_reader_options_builder{}.timestamp_type(
+                 cudf::data_type{cudf::type_id::TIMESTAMP_DAYS}),
+               cudf::logic_error);
+}
+
 TEST_F(OrcReaderTest, SingleInputs)
 {
   srand(31533);

cpp/tests/io/parquet_reader_test.cpp

@@ -1011,6 +1011,31 @@ TEST_F(ParquetReaderTest, SelectColumnByMissingFieldIds)
   }
 }
 
+TEST_F(ParquetReaderTest, TimestampTypeMustHaveSecondBasedUnit)
+{
+  // The reader rescales timestamps by a clock rate in ticks per second, which TIMESTAMP_DAYS
+  // cannot express: a request for it used to decode seconds as 8-byte values into a column
+  // allocated at 4 bytes per row.
+  auto options = cudf::io::parquet_reader_options{};
+  for (auto const id : {cudf::type_id::EMPTY,
+                        cudf::type_id::TIMESTAMP_SECONDS,
+                        cudf::type_id::TIMESTAMP_MILLISECONDS,
+                        cudf::type_id::TIMESTAMP_MICROSECONDS,
+                        cudf::type_id::TIMESTAMP_NANOSECONDS}) {
+    EXPECT_NO_THROW(options.set_timestamp_type(cudf::data_type{id}));
+    EXPECT_EQ(options.get_timestamp_type().id(), id);
+  }
+  for (auto const id :
+       {cudf::type_id::TIMESTAMP_DAYS, cudf::type_id::DURATION_SECONDS, cudf::type_id::INT64}) {
+    EXPECT_THROW(options.set_timestamp_type(cudf::data_type{id}), cudf::logic_error);
+  }
+  // A rejected type leaves the previous one in place.
+  EXPECT_EQ(options.get_timestamp_type().id(), cudf::type_id::TIMESTAMP_NANOSECONDS);
+  EXPECT_THROW(cudf::io::parquet_reader_options_builder{}.timestamp_type(
+                 cudf::data_type{cudf::type_id::TIMESTAMP_DAYS}),
+               cudf::logic_error);
+}
+
 TEST_F(ParquetReaderTest, ColumnSelectionModesAreExclusive)
 {
   auto selected_by_name = cudf::io::parquet_reader_options{};

java/src/main/java/ai/rapids/cudf/ORCOptions.java

@@ -1,6 +1,6 @@
 /*
  *
- *  SPDX-FileCopyrightText: Copyright (c) 2019-2025, NVIDIA CORPORATION.
+ *  SPDX-FileCopyrightText: Copyright (c) 2019-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
  *  SPDX-License-Identifier: Apache-2.0
  *
  */
@@ -73,11 +73,13 @@ public Builder withNumPyTypes(boolean useNumPyTypes) {
 
     /**
      * Specify the time unit to use when returning timestamps.
+     * Only TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS, TIMESTAMP_MICROSECONDS and
+     * TIMESTAMP_NANOSECONDS are valid; for TIMESTAMP_DAYS, cast the returned column instead.
      * @param unit default unit of time specified by the user
      * @return builder for chaining
      */
     public ORCOptions.Builder withTimeUnit(DType unit) {
-      assert unit.isTimestampType();
+      assert unit == DType.EMPTY || unit.hasTimeResolution();
       this.unit = unit;
       return this;
     }

java/src/main/java/ai/rapids/cudf/ParquetOptions.java

@@ -1,6 +1,6 @@
 /*
  *
- *  SPDX-FileCopyrightText: Copyright (c) 2019, NVIDIA CORPORATION.
+ *  SPDX-FileCopyrightText: Copyright (c) 2019-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
  *  SPDX-License-Identifier: Apache-2.0
  *
  */
@@ -48,11 +48,13 @@ public static class Builder extends ColumnFilterOptions.Builder<Builder> {
 
     /**
      * Specify the time unit to use when returning timestamps.
+     * Only TIMESTAMP_SECONDS, TIMESTAMP_MILLISECONDS, TIMESTAMP_MICROSECONDS and
+     * TIMESTAMP_NANOSECONDS are valid; for TIMESTAMP_DAYS, cast the returned column instead.
      * @param unit default unit of time specified by the user
      * @return builder for chaining
      */
     public Builder withTimeUnit(DType unit) {
-      assert unit.isTimestampType();
+      assert unit == DType.EMPTY || unit.hasTimeResolution();
       this.unit = unit;
       return this;
     }