add conv for bit

Author: elianddb

enginetest/queries/script_queries.go

@@ -134,6 +134,7 @@ var ScriptTests = []ScriptTest{
 					UNION ALL  
 					SELECT 48 FROM report_card WHERE id = 1`,
 				Expected:                      []sql.Row{{int64(0)}, {int64(48)}},
+				// Server engine returns BIT over the wire as []byte/unsigned, so skip result check here
 				SkipResultCheckOnServerEngine: true,
 			},
 		},
@@ -183,8 +184,8 @@ var ScriptTests = []ScriptTest{
 					WHERE archived = FALSE AND id <> 1
 				) AS dummy_alias`,
 				Expected: []sql.Row{
-					{int64(5), int64(1), "Card1", int64(0), uint64(0), int64(2)},
-					{int64(7), int64(2), "Collection1", int64(0), nil, int64(2)},
+					{int64(5), int64(1), "Card1", uint64(0), int64(0), int64(2)},
+					{int64(7), int64(2), "Collection1", uint64(0), nil, int64(2)},
 				},
 				SkipResultCheckOnServerEngine: true,
 			},

sql/expression/convert.go

@@ -123,6 +123,9 @@ func GetConvertToType(l, r sql.Type) string {
 	if types.IsDecimal(l) || types.IsDecimal(r) {
 		return ConvertToDecimal
 	}
+	if types.IsBit(l) || types.IsBit(r) {
+		return ConvertToSigned
+	}
 	if types.IsUnsigned(l) && types.IsUnsigned(r) {
 		return ConvertToUnsigned
 	}

sql/plan/set_op.go

@@ -19,6 +19,7 @@ import (
 	"strings"
 
 	"github.com/dolthub/go-mysql-server/sql"
+	"github.com/dolthub/go-mysql-server/sql/types"
 )
 
 const (
@@ -100,6 +101,7 @@ func (s *SetOp) Schema() sql.Schema {
 	for i := range ls {
 		c := *ls[i]
 		if i < len(rs) {
+			c.Type = types.GeneralizeTypes(ls[i].Type, rs[i].Type)
 			c.Nullable = ls[i].Nullable || rs[i].Nullable
 		}
 		ret[i] = &c