fix server errs

Author: elianddb

enginetest/queries/script_queries.go

@@ -129,7 +129,7 @@ var ScriptTests = []ScriptTest{
 		},
 		Assertions: []ScriptTestAssertion{
 			{
-				// Test UNION with BIT column and integer constant (related to customer's "48 is beyond maximum value" error)
+				// Reproduces customer's "48 is beyond maximum value" error when BIT and integer constants are UNIONed
 				Query: `SELECT archived FROM report_card WHERE id = 1
 					UNION ALL  
 					SELECT 48 FROM report_card WHERE id = 1`,
@@ -181,8 +181,8 @@ var ScriptTests = []ScriptTest{
 					WHERE archived = FALSE AND id <> 1
 				) AS dummy_alias`,
 				Expected: []sql.Row{
-					{int64(5), int64(1), "Card1", uint64(0), int64(0), int64(2)},
-					{int64(7), int64(2), "Collection1", uint64(0), nil, int64(2)},
+					{int64(5), int64(1), "Card1", int64(0), int64(0), int64(2)},
+					{int64(7), int64(2), "Collection1", int64(0), nil, int64(2)},
 				},
 			},
 		},

sql/analyzer/resolve_unions.go

@@ -100,7 +100,7 @@ func finalizeUnions(ctx *sql.Context, a *Analyzer, n sql.Node, scope *plan.Scope
 			return nil, transform.SameTree, err
 		}
 
-		// UNION operations can return multiple rows, so Max1Row optimization is invalid
+		// UNION can return multiple rows even when child queries use LIMIT 1, so disable Max1Row optimization
 		qFlags.Unset(sql.QFlagMax1Row)
 
 		return newN, transform.NewTree, nil

sql/iters/rel_iters.go

@@ -601,8 +601,9 @@ func (di *distinctIter) Dispose() {
 }
 
 type UnionIter struct {
-	Cur      sql.RowIter
-	NextIter func(ctx *sql.Context) (sql.RowIter, error)
+	Cur          sql.RowIter
+	NextIter     func(ctx *sql.Context) (sql.RowIter, error)
+	ResultSchema sql.Schema
 }
 
 func (ui *UnionIter) Next(ctx *sql.Context) (sql.Row, error) {
@@ -620,8 +621,23 @@ func (ui *UnionIter) Next(ctx *sql.Context) (sql.Row, error) {
 		if err != nil {
 			return nil, err
 		}
-		return ui.Cur.Next(ctx)
+		res, err = ui.Cur.Next(ctx)
+		if err != nil {
+			return nil, err
+		}
+	}
+	
+	// Convert BIT values to Int64 when schema generalization changed types for server engine compatibility
+	if ui.ResultSchema != nil {
+		for i, val := range res {
+			if i < len(ui.ResultSchema) && val != nil {
+				if converted, _, err := ui.ResultSchema[i].Type.Convert(ctx, val); err == nil {
+					res[i] = converted
+				}
+			}
+		}
 	}
+	
 	return res, err
 }
 

sql/rowexec/rel.go

@@ -814,6 +814,7 @@ func (b *BaseBuilder) buildSetOp(ctx *sql.Context, s *plan.SetOp, row sql.Row) (
 			NextIter: func(ctx *sql.Context) (sql.RowIter, error) {
 				return b.buildNodeExec(ctx, s.Right(), row)
 			},
+			ResultSchema: s.Schema(),
 		}
 	case plan.IntersectType:
 		var iter2 sql.RowIter

sql/types/bit.go

@@ -193,6 +193,11 @@ func (t BitType_) SQL(ctx *sql.Context, dest []byte, v interface{}) (sqltypes.Va
 	if v == nil {
 		return sqltypes.NULL, nil
 	}
+	
+	// Delegate int64 values to Int64.SQL to prevent server engine []uint8 serialization errors
+	if int64Val, ok := v.(int64); ok {
+		return Int64.SQL(ctx, dest, int64Val)
+	}
 	value, _, err := t.Convert(ctx, v)
 	if err != nil {
 		return sqltypes.Value{}, err

sql/types/conversion.go

@@ -637,6 +637,11 @@ func generalizeNumberTypes(a, b sql.Type) sql.Type {
 // TODO: Create and handle "Illegal mix of collations" error
 // TODO: Handle extended types, like DoltgresType
 func GeneralizeTypes(a, b sql.Type) sql.Type {
+	// BIT types must convert to Int64 in UNION to avoid server engine serialization errors with []uint8
+	if (IsBit(a) || IsBit(b)) && (IsBit(a) && IsBit(b) || IsNullType(a) || IsNullType(b)) {
+		return Int64
+	}
+	
 	if reflect.DeepEqual(a, b) {
 		return a
 	}
@@ -693,18 +698,6 @@ func GeneralizeTypes(a, b sql.Type) sql.Type {
 		return LongBlob
 	}
 
-	aIsBit := IsBit(a)
-	bIsBit := IsBit(b)
-	if aIsBit && bIsBit {
-		// TODO: match max bits to max of max bits between a and b
-		return a.Promote()
-	}
-	if aIsBit {
-		a = Int64
-	}
-	if bIsBit {
-		b = Int64
-	}
 
 	aIsYear := IsYear(a)
 	bIsYear := IsYear(b)