evalengine bugfix: handle nil evals correctly when coercing values (#…

…14906)

Signed-off-by: Andres Taylor <[email protected]>

go/vt/vtgate/evalengine/api_arithmetic_test.go

@@ -24,16 +24,14 @@ import (
 	"strconv"
 	"testing"
 
-	"vitess.io/vitess/go/test/utils"
-	"vitess.io/vitess/go/vt/vthash"
-
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"vitess.io/vitess/go/sqltypes"
-
+	"vitess.io/vitess/go/test/utils"
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
 	"vitess.io/vitess/go/vt/vterrors"
+	"vitess.io/vitess/go/vt/vthash"
 )
 
 var (
@@ -740,6 +738,23 @@ func TestToSqlValue(t *testing.T) {
 		typ: sqltypes.Decimal,
 		v:   newEvalFloat(1.2e-16),
 		out: TestValue(sqltypes.Decimal, "0.00000000000000012"),
+	}, {
+		// null in should return null out no matter what type
+		typ: sqltypes.Int64,
+		v:   nil,
+		out: sqltypes.NULL,
+	}, {
+		typ: sqltypes.Uint64,
+		v:   nil,
+		out: sqltypes.NULL,
+	}, {
+		typ: sqltypes.Float64,
+		v:   nil,
+		out: sqltypes.NULL,
+	}, {
+		typ: sqltypes.VarChar,
+		v:   nil,
+		out: sqltypes.NULL,
 	}}
 	for _, tcase := range tcases {
 		got := evalToSQLValueWithType(tcase.v, tcase.typ)

go/vt/vtgate/evalengine/eval.go

@@ -128,7 +128,7 @@ func evalToSQLValueWithType(e eval, resultType sqltypes.Type) sqltypes.Value {
 		case *evalDecimal:
 			return sqltypes.MakeTrusted(resultType, e.dec.FormatMySQL(e.length))
 		}
-	default:
+	case e != nil:
 		return sqltypes.MakeTrusted(resultType, e.ToRawBytes())
 	}
 	return sqltypes.NULL