Cast only time of day to nanos to avoid an overflow in Parquet INT96 write

cpp/src/io/parquet/page_enc.cu

@@ -933,22 +933,23 @@ constexpr auto julian_calendar_epoch_diff()
 }
 
 /**
- * @brief Converts a timestamp_ns into a pair with nanoseconds since midnight and number of Julian
- * days. Does not deal with time zones. Used by INT96 code.
+ * @brief Converts number of periods Per into a pair with nanoseconds since midnight
+ * and number of Julian days. Does not deal with time zones. Used by INT96 code.
  *
- * @param ns number of nanoseconds since epoch
+ * @param v int64_t count of ticks since epoch
  * @return std::pair<nanoseconds,days> where nanoseconds is the number of nanoseconds
  * elapsed in the day and days is the number of days from Julian epoch.
  */
-static __device__ std::pair<duration_ns, duration_D> convert_nanoseconds(timestamp_ns const ns)
+template <typename Per>
+__device__ auto juilian_days_with_time(int64_t v)
 {
   using namespace cuda::std::chrono;
-  auto const nanosecond_ticks = ns.time_since_epoch();
-  auto const gregorian_days   = floor<days>(nanosecond_ticks);
-  auto const julian_days      = gregorian_days + ceil<days>(julian_calendar_epoch_diff());
-
-  auto const last_day_ticks = nanosecond_ticks - gregorian_days;
-  return {last_day_ticks, julian_days};
+  auto const dur_total             = duration<int64_t, Per>{v};
+  auto const dur_days              = floor<days>(dur_total);
+  auto const dur_time_of_day       = dur_total - dur_days;
+  auto const dur_time_of_day_nanos = duration_cast<nanoseconds>(dur_time_of_day);
+  auto const julian_days           = dur_days + ceil<days>(julian_calendar_epoch_diff());
+  return std::make_pair(dur_time_of_day_nanos, julian_days);
 }
 
 // blockDim(128, 1, 1)
@@ -1236,22 +1237,23 @@ __global__ void __launch_bounds__(128, 8)
               }
             }
 
-            auto const ret = convert_nanoseconds([&]() {
+            auto const& [last_day_nanos, julian_days] = ([&]() {
+              using namespace cuda::std::chrono;
               switch (s->col.leaf_column->type().id()) {
                 case type_id::TIMESTAMP_SECONDS:
                 case type_id::TIMESTAMP_MILLISECONDS: {
-                  return timestamp_ns{duration_ms{v}};
+                  return juilian_days_with_time<cuda::std::milli>(v);
                 } break;
                 case type_id::TIMESTAMP_MICROSECONDS:
                 case type_id::TIMESTAMP_NANOSECONDS: {
-                  return timestamp_ns{duration_us{v}};
+                  return juilian_days_with_time<cuda::std::micro>(v);
                 } break;
               }
-              return timestamp_ns{duration_ns{0}};
+              return juilian_days_with_time<cuda::std::nano>(0);
             }());
 
             // the 12 bytes of fixed length data.
-            v             = ret.first.count();
+            v             = last_day_nanos.count();
             dst[pos + 0]  = v;
             dst[pos + 1]  = v >> 8;
             dst[pos + 2]  = v >> 16;
@@ -1260,7 +1262,7 @@ __global__ void __launch_bounds__(128, 8)
             dst[pos + 5]  = v >> 40;
             dst[pos + 6]  = v >> 48;
             dst[pos + 7]  = v >> 56;
-            uint32_t w    = ret.second.count();
+            uint32_t w    = julian_days.count();
             dst[pos + 8]  = w;
             dst[pos + 9]  = w >> 8;
             dst[pos + 10] = w >> 16;

cpp/tests/io/parquet_test.cpp

@@ -38,6 +38,7 @@
 #include <cudf/transform.hpp>
 #include <cudf/unary.hpp>
 #include <cudf/utilities/span.hpp>
+#include <cudf/wrappers/timestamps.hpp>
 
 #include <src/io/parquet/compact_protocol_reader.hpp>
 #include <src/io/parquet/parquet.hpp>
@@ -6411,4 +6412,28 @@ TEST_F(ParquetReaderTest, FilterFloatNAN)
   CUDF_TEST_EXPECT_TABLES_EQUAL(expected1->view(), result1);
 }
 
+TEST_F(ParquetWriterTest, TimestampMicrosINT96NoOverflow)
+{
+  using namespace cuda::std::chrono;
+  using namespace cudf::io;
+
+  column_wrapper<cudf::timestamp_us> big_ts_col{
+    sys_days{year{3023} / month{7} / day{14}} + 7h + 38min + 45s + 418688us,
+    sys_days{year{723} / month{3} / day{21}} + 14h + 20min + 13s + microseconds{781ms}};
+
+  table_view expected({big_ts_col});
+  auto filepath = temp_env->get_temp_filepath("BigINT96Timestamp.parquet");
+
+  auto const out_opts =
+    parquet_writer_options::builder(sink_info{filepath}, expected).int96_timestamps(true).build();
+  write_parquet(out_opts);
+
+  auto const in_opts = parquet_reader_options::builder(source_info(filepath))
+                         .timestamp_type(cudf::data_type(cudf::type_id::TIMESTAMP_MICROSECONDS))
+                         .build();
+  auto const result = read_parquet(in_opts);
+
+  CUDF_TEST_EXPECT_TABLES_EQUAL(expected, result.tbl->view());
+}
+
 CUDF_TEST_PROGRAM_MAIN()