Merge #47483

47483: sql: fix casting of negative datums to decimals r=rytaft a=rytaft

Prior to this commit, when negative intervals, timestamps, and timestamptzs
were cast to decimals, the result was incorrect. The problem was due to the
fact that for these negative values, `Decimal.Coeff.neg` was being set to true,
while `Decimal.Negative` was false. As explained in the comment in `decimal.go`,
"Coeff must be positive. If it is negative results may be incorrect and apd
may panic."

This commit fixes the problem by setting `Decimal.Negative` to true and
`Decimal.Coeff.neg` to false when casting negative datums to decimals.

Fixes #47327

Release note (bug fix): Fixed incorrect results that could occur when
casting negative intervals or timestamps to type decimal.

Co-authored-by: Rebecca Taft <[email protected]>

pkg/sql/logictest/testdata/logic_test/cast

@@ -12,3 +12,20 @@ CREATE TABLE t2 AS SELECT 18446744073709551616::FLOAT AS f
 
 statement error pgcode 22003 integer out of range
 SELECT f::int FROM t2
+
+# Regression test for #47327. Test that negative intervals are correctly
+# cast to a decimal.
+statement ok
+CREATE TABLE t0(c0 DECIMAL UNIQUE); INSERT INTO t0(c0) VALUES(0);
+
+statement ok
+CREATE TABLE t1(c0 DECIMAL); INSERT INTO t1(c0) VALUES(0);
+
+# Both of these queries should return no rows.
+query T
+SELECT t0.c0 FROM t0 WHERE t0.c0 BETWEEN t0.c0 AND INTERVAL '-1'::DECIMAL
+----
+
+query T
+SELECT t1.c0 FROM t1 WHERE t1.c0 BETWEEN t1.c0 AND INTERVAL '-1'::DECIMAL
+----

pkg/sql/opt/exec/execbuilder/testdata/scalar

@@ -751,3 +751,17 @@ root                      ·              ·                             ("array
                 └── scan  ·              ·                             (a, b)     ·
 ·                         table          t@primary                     ·          ·
 ·                         spans          FULL SCAN                     ·          ·
+
+# Regression test for #47327. The span should have an end value of -1.
+statement ok
+CREATE TABLE t0(c0 DECIMAL UNIQUE); INSERT INTO t0(c0) VALUES(0);
+
+query TTTTT
+EXPLAIN (VERBOSE) SELECT t0.c0 FROM t0 WHERE t0.c0 BETWEEN t0.c0 AND INTERVAL '-1'::DECIMAL
+----
+·     distributed  false                 ·     ·
+·     vectorized   true                  ·     ·
+scan  ·            ·                     (c0)  ·
+·     table        t0@t0_c0_key          ·     ·
+·     spans        /!NULL-/-1/PrefixEnd  ·     ·
+·     filter       c0 >= c0              ·     ·

pkg/sql/sem/tree/eval.go

@@ -2983,6 +2983,11 @@ func TimestampToDecimal(ts hlc.Timestamp) *DDecimal {
 	val.Mul(val, big10E10)
 	val.Add(val, big.NewInt(int64(ts.Logical)))
 
+	// val must be positive. If it was set to a negative value above,
+	// transfer the sign to res.Negative.
+	res.Negative = val.Sign() < 0
+	val.Abs(val)
+
 	// Shift 10 decimals to the right, so that the logical
 	// field appears as fractional part.
 	res.Decimal.Exponent = -10
@@ -3494,6 +3499,12 @@ func PerformCast(ctx *EvalContext, d Datum, t *types.T) (Datum, error) {
 			return nil, err
 		}
 		if !unset {
+			// dd.Coeff must be positive. If it was set to a negative value
+			// above, transfer the sign to dd.Negative.
+			if dd.Coeff.Sign() < 0 {
+				dd.Negative = true
+				dd.Coeff.Abs(&dd.Coeff)
+			}
 			err = LimitDecimalWidth(&dd.Decimal, int(t.Precision()), int(t.Scale()))
 			return &dd, err
 		}

pkg/sql/sem/tree/testdata/eval/cast

@@ -1054,3 +1054,19 @@ eval
 '0101000000000000000000F03F000000000000F03F'::geometry::geography
 ----
 '0101000020E6100000000000000000F03F000000000000F03F'
+
+# Test that decimals are correctly cast when the original value is negative.
+eval
+'-2020-10-10'::timestamp::decimal
+----
+-125887824000.000000
+
+eval
+'-2020-10-10-2020 10:10:00.11111111111111111'::timestamptz::decimal
+----
+-125887714199.888889
+
+eval
+'-10'::interval::decimal
+----
+-10.000000000