Fix bug of datetime64 parsed from string '1969-12-31 23:59:59.123' (#37039)

src/Core/DecimalFunctions.h

@@ -156,7 +156,7 @@ inline DecimalComponents<DecimalType> splitWithScaleMultiplier(
     using T = typename DecimalType::NativeType;
     const auto whole = decimal.value / scale_multiplier;
     auto fractional = decimal.value % scale_multiplier;
-    if (fractional < T(0))
+    if (whole && fractional < T(0))
         fractional *= T(-1);
 
     return {whole, fractional};
@@ -199,7 +199,7 @@ inline typename DecimalType::NativeType getFractionalPartWithScaleMultiplier(
     /// Anycase we make modulo before compare to make scale_multiplier > 1 unaffected.
     T result = decimal.value % scale_multiplier;
     if constexpr (!keep_sign)
-        if (result < T(0))
+        if (decimal.value / scale_multiplier && result < T(0))
             result = -result;
 
     return result;

src/Core/tests/gtest_DecimalFunctions.cpp

@@ -176,7 +176,7 @@ INSTANTIATE_TEST_SUITE_P(Basic,
             }
         },
         {
-            "When scale is not 0 and whole part is 0.",
+            "For positive Decimal value, with scale not 0, and whole part is 0.",
             123,
             3,
             {
@@ -184,6 +184,16 @@ INSTANTIATE_TEST_SUITE_P(Basic,
                 123
             }
         },
+        {
+            "For negative Decimal value, with scale not 0, and whole part is 0.",
+            -123,
+            3,
+            {
+                0,
+                -123
+            }
+        },
+
         {
             "For negative Decimal value whole part is negative, fractional is non-negative.",
             -1234567'89,
@@ -216,6 +226,24 @@ INSTANTIATE_TEST_SUITE_P(Basic,
                 187618332,
                 123
             }
+        },
+        {
+            "Negative timestamp 1969-12-31 23:59:59.123 UTC",
+            DateTime64(-877),
+            3,
+            {
+                0,
+                -877
+            }
+        },
+        {
+            "Positive timestamp 1970-01-01 00:00:00.123 UTC",
+            DateTime64(123),
+            3,
+            {
+                0,
+                123
+            }
         }
     })
 );

src/IO/ReadHelpers.h

@@ -931,12 +931,29 @@ inline ReturnType readDateTimeTextImpl(DateTime64 & datetime64, UInt32 scale, Re
             ++buf.position();
 
         /// Keep sign of fractional part the same with whole part if datetime64 is negative
-        /// 1965-12-12 12:12:12.123 => whole = -127914468, fraction = 123(sign>0) -> new whole = -127914467, new fraction = 877(sign<0)
+        /// Case1:
+        ///     1965-12-12 12:12:12.123
+        ///     => whole = -127914468, fractional = 123(coefficient>0)
+        ///     => new whole = -127914467, new fractional = 877(coefficient<0)
+        ///
+        /// Case2:
+        ///     1969-12-31 23:59:59.123
+        ///     => whole = -1, fractional = 123(coefficient>0)
+        ///     => new whole = 0, new fractional = -877(coefficient>0)
         if (components.whole < 0 && components.fractional != 0)
         {
             const auto scale_multiplier = DecimalUtils::scaleMultiplier<DateTime64::NativeType>(scale);
             ++components.whole;
-            components.fractional = scale_multiplier - components.fractional;
+            if (components.whole)
+            {
+                /// whole keep the sign, fractional should be non-negative
+                components.fractional = scale_multiplier - components.fractional;
+            }
+            else
+            {
+                /// when whole is zero, fractional should keep the sign
+                components.fractional = components.fractional - scale_multiplier;
+            }
         }
     }
     /// 9908870400 is time_t value for 2184-01-01 UTC (a bit over the last year supported by DateTime64)

src/IO/WriteHelpers.h

@@ -805,11 +805,21 @@ inline void writeDateTimeText(DateTime64 datetime64, UInt32 scale, WriteBuffer &
     scale = scale > MaxScale ? MaxScale : scale;
 
     auto components = DecimalUtils::split(datetime64, scale);
-    /// -127914467.877 => whole = -127914467, fraction = 877 => new whole = -127914468(1965-12-12 12:12:12), new fraction = 123(.123) => 1965-12-12 12:12:12.123
-    if (components.whole < 0 && components.fractional != 0)
+    /// Case1:
+    /// -127914467.877
+    /// => whole = -127914467, fraction = 877(After DecimalUtils::split)
+    /// => new whole = -127914468(1965-12-12 12:12:12), new fraction = 1000 - 877 = 123(.123)
+    /// => 1965-12-12 12:12:12.123
+    ///
+    /// Case2:
+    /// -0.877
+    /// => whole = 0, fractional = -877(After DecimalUtils::split)
+    /// => whole = -1(1969-12-31 23:59:59), fractional = 1000 + (-877) = 123(.123)
+    using T = typename DateTime64::NativeType;
+    if (datetime64.value < 0 && components.fractional)
     {
+        components.fractional = DecimalUtils::scaleMultiplier<T>(scale) + (components.whole ? T(-1) : T(1)) * components.fractional;
         --components.whole;
-        components.fractional = DecimalUtils::scaleMultiplier<DateTime64::NativeType>(scale) - components.fractional;
     }
 
     writeDateTimeText<date_delimeter, time_delimeter, between_date_time_delimiter>(LocalDateTime(components.whole, time_zone), buf);
@@ -989,7 +999,12 @@ void writeText(Decimal<T> x, UInt32 scale, WriteBuffer & ostr, bool trailing_zer
     {
         part = DecimalUtils::getFractionalPart(x, scale);
         if (part || trailing_zeros)
+        {
+            if (part < 0)
+                part *= T(-1);
+
             writeDecimalFractional(part, scale, ostr, trailing_zeros);
+        }
     }
 }
 

tests/queries/0_stateless/02242_negative_datetime64.reference

@@ -1,2 +1,3 @@
 -127914467.877
 187618332.123
+1969-12-31 23:59:59.123

tests/queries/0_stateless/02242_negative_datetime64.sql

@@ -1,2 +1,3 @@
 SELECT  cast(toDateTime64('1965-12-12 12:12:12.123', 3, 'UTC') as Decimal64(3));
 SELECT  cast(toDateTime64('1975-12-12 12:12:12.123', 3, 'UTC') as Decimal64(3));
+SELECT  toDateTime64('1969-12-31 23:59:59.123', 3, 'UTC');