sql: improve interval math for div and mul

In #37582 we added correct `interval * float` semantics. Here we extend that to float division. In addition, change int division to be a wrapper around float division so that remainders are correctly handled. Int multiply has no need to change since it's lossless. Release note (sql change): Correct interval math when multiplying or dividing by floats or ints.
cockroachdb · May 22, 2019 · 567a5fe · 567a5fe
1 parent 51a5dc9
commit 567a5fe
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Showing 3 changed files with 54 additions and 8 deletions.
diff --git a/pkg/sql/logictest/testdata/logic_test/datetime b/pkg/sql/logictest/testdata/logic_test/datetime
@@ -1350,3 +1350,31 @@ SELECT '-239852040018-04-28':::DATE
 
 statement error out of range
 SELECT(7133080445639580613::INT8 + '1977-11-03'::DATE) = '-239852040018-04-28':::DATE
+
+subtest interval_math
+
+query TTTTTTT
+SELECT
+    i,
+    i / 2::INT8,
+    i * 2::INT8,
+    i / 2::FLOAT8,
+    i * 2::FLOAT8,
+    i / .2362::FLOAT8,
+    i * .2362::FLOAT8
+FROM
+    (
+        VALUES
+            ('1 day'::INTERVAL),
+            ('1 month'::INTERVAL),
+            ('1 hour'::INTERVAL),
+            ('1 month 2 days 4 hours'::INTERVAL)
+    )
+        AS v (i)
+ORDER BY
+    i
+----
+01:00:00               00:30:00          02:00:00                00:30:00          02:00:00                04:14:01.320914                 00:14:10.32
+1 day                  12:00:00          2 days                  12:00:00          2 days                  4 days 05:36:31.701948          05:40:07.68
+1 mon                  15 days           2 mons                  15 days           2 mons                  4 mons 7 days 00:15:51.058425   7 days 02:03:50.4
+1 mon 2 days 04:00:00  16 days 02:00:00  2 mons 4 days 08:00:00  16 days 02:00:00  2 mons 4 days 08:00:00  4 mons 15 days 28:24:59.745978  7 days 14:20:47.04
diff --git a/pkg/util/duration/duration.go b/pkg/util/duration/duration.go
@@ -480,7 +480,7 @@ func (d Duration) Mul(x int64) Duration {
 
 // Div returns a Duration representing a time length of d/x.
 func (d Duration) Div(x int64) Duration {
-	return MakeDuration(d.nanos/x, d.Days/x, d.Months/x)
+	return d.DivFloat(float64(x))
 }
 
 // MulFloat returns a Duration representing a time length of d*x.
@@ -497,10 +497,13 @@ func (d Duration) MulFloat(x float64) Duration {
 
 // DivFloat returns a Duration representing a time length of d/x.
 func (d Duration) DivFloat(x float64) Duration {
+	monthInt, monthFrac := math.Modf(float64(d.Months) / x)
+	dayInt, dayFrac := math.Modf((float64(d.Days) / x) + (monthFrac * daysInMonth))
+
 	return MakeDuration(
-		int64(float64(d.nanos)/x),
-		int64(float64(d.Days)/x),
-		int64(float64(d.Months)/x),
+		int64((float64(d.nanos)/x)+(dayFrac*float64(nanosInDay))),
+		int64(dayInt),
+		int64(monthInt),
 	)
 }
 

diff --git a/pkg/util/duration/duration_test.go b/pkg/util/duration/duration_test.go
@@ -344,50 +344,65 @@ func TestAddMicros(t *testing.T) {
 	}
 }
 
-func TestMulFloat(t *testing.T) {
+func TestFloatMath(t *testing.T) {
 	const nanosInMinute = nanosInSecond * 60
 	const nanosInHour = nanosInMinute * 60
 
 	tests := []struct {
 		d   Duration
 		f   float64
-		res Duration
+		mul Duration
+		div Duration
 	}{
 		{
 			Duration{Months: 1, Days: 2, nanos: nanosInHour * 2},
 			0.15,
 			Duration{Days: 4, nanos: nanosInHour*19 + nanosInMinute*30},
+			Duration{Months: 6, Days: 33, nanos: nanosInHour*21 + nanosInMinute*20},
 		},
 		{
 			Duration{Months: 1, Days: 2, nanos: nanosInHour * 2},
 			0.3,
 			Duration{Days: 9, nanos: nanosInHour * 15},
+			Duration{Months: 3, Days: 16, nanos: nanosInHour*22 + nanosInMinute*40},
 		},
 		{
 			Duration{Months: 1, Days: 2, nanos: nanosInHour * 2},
 			0.5,
 			Duration{Days: 16, nanos: nanosInHour * 1},
+			Duration{Months: 2, Days: 4, nanos: nanosInHour * 4},
 		},
 		{
 			Duration{Months: 1, Days: 2, nanos: nanosInHour * 2},
 			0.8,
 			Duration{Days: 25, nanos: nanosInHour * 16},
+			Duration{Months: 1, Days: 10, nanos: nanosInHour*2 + nanosInMinute*30},
 		},
 		{
 			Duration{Months: 1, Days: 17, nanos: nanosInHour * 2},
 			2.0,
 			Duration{Months: 2, Days: 34, nanos: nanosInHour * 4},
+			Duration{Days: 23, nanos: nanosInHour * 13},
 		},
 	}
 
 	for i, test := range tests {
-		if res := test.d.MulFloat(test.f); test.res != res {
+		if res := test.d.MulFloat(test.f); test.mul != res {
 			t.Errorf(
 				"%d: expected %v.MulFloat(%f) = %v, found %v",
 				i,
 				test.d,
 				test.f,
-				test.res,
+				test.mul,
+				res)
+		}
+		if res := test.d.DivFloat(test.f); test.div != res {
+			t.Errorf(
+				"%d: expected %v.DivFloat(%f) = %v, found %v",
+				i,
+				test.d,
+				test.f,
+				test.div,
 				res)
 		}
 	}