fix: Parsing of fractions of a second in parse_datetime() (#11723)

Summary: Pull Request resolved: #11723 A bug causes function to return wrong fractions of a second in some cases. Reviewed By: gggrace14 Differential Revision: D66688586 fbshipit-source-id: 3a2308026c5484f9ec4f87679ec9cae3512d8fb4
facebookincubator · Dec 3, 2024 · a94e870 · a94e870
1 parent a0bbea2
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Showing 2 changed files with 37 additions and 3 deletions.
diff --git a/velox/functions/lib/DateTimeFormatter.cpp b/velox/functions/lib/DateTimeFormatter.cpp
@@ -904,9 +904,7 @@ int32_t parseFromPattern(
       int count = 0;
       while (cur < end && cur < startPos + maxDigitConsume &&
              characterIsDigit(*cur)) {
-        if (count < 3) {
-          number = number * 10 + (*cur - '0');
-        }
+        number = number * 10 + (*cur - '0');
         ++cur;
         ++count;
       }

diff --git a/velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp b/velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp
@@ -3185,6 +3185,42 @@ TEST_F(DateTimeFunctionsTest, dateDiffTimestampWithTimezone) {
           "2023-03-11 00:00:00 America/Los_Angeles"));
 }
 
+TEST_F(DateTimeFunctionsTest, parseDatetimeRoundtrip) {
+  const auto parseDatetimeRoundTrip =
+      [&](const std::optional<std::string>& input,
+          const std::optional<std::string>& format) {
+        return evaluateOnce<std::string>(
+            "cast(parse_datetime(c0, c1) as varchar)", input, format);
+      };
+
+  EXPECT_EQ(
+      "2024-01-20 01:00:30.127 UTC",
+      parseDatetimeRoundTrip(
+          "2024-01-20 01:00:30.12700", "yyyy-MM-dd HH:mm:ss.SSSSS"));
+  EXPECT_EQ(
+      "2024-01-20 01:00:30.459 UTC",
+      parseDatetimeRoundTrip(
+          "2024-01-20 01:00:30.45900000", "yyyy-MM-dd HH:mm:ss.SSSSSSSS"));
+  EXPECT_EQ(
+      "2024-01-20 01:00:30.617 UTC",
+      parseDatetimeRoundTrip(
+          "2024-01-20 01:00:30.6170", "yyyy-MM-dd HH:mm:ss.SSSSSSSS"));
+
+  EXPECT_EQ(
+      "2024-01-20 01:00:30.127 UTC",
+      parseDatetimeRoundTrip(
+          "2024-01-20 01:00:30.127149", "yyyy-MM-dd HH:mm:ss.SSSSSS"));
+  EXPECT_EQ(
+      "2024-01-20 01:00:30.127 UTC",
+      parseDatetimeRoundTrip(
+          "2024-01-20 01:00:30.127941", "yyyy-MM-dd HH:mm:ss.SSSSSS"));
+
+  VELOX_ASSERT_THROW(
+      parseDatetimeRoundTrip(
+          "2024-01-20 01:00:30.6170", "yyyy-MM-dd HH:mm:ss.SSS"),
+      "Invalid date format");
+}
+
 TEST_F(DateTimeFunctionsTest, parseDatetime) {
   const auto parseDatetime = [&](const std::optional<std::string>& input,
                                  const std::optional<std::string>& format) {