Fix #9428: Allow default keyword as value for generated columns.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: elianddb

enginetest/queries/generated_columns.go

@@ -65,6 +65,14 @@ var GeneratedColumnTests = []ScriptTest{
 				Query:    "select * from t1 where b = 5 order by a",
 				Expected: []sql.Row{{4, 5}},
 			},
+			{
+				Query:    "insert into t1 values (5, DEFAULT)",
+				Expected: []sql.Row{{types.NewOkResult(1)}},
+			},
+			{
+				Query:    "select * from t1 where a = 5",
+				Expected: []sql.Row{{5, 6}},
+			},
 			{
 				Query:       "update t1 set b = b + 1",
 				ExpectedErr: sql.ErrGeneratedColumnValue,
@@ -75,15 +83,43 @@ var GeneratedColumnTests = []ScriptTest{
 			},
 			{
 				Query:    "select * from t1 order by a",
-				Expected: []sql.Row{{2, 3}, {3, 4}, {4, 5}, {10, 11}},
+				Expected: []sql.Row{{2, 3}, {3, 4}, {4, 5}, {5, 6}, {10, 11}},
 			},
 			{
 				Query:    "delete from t1 where b = 11",
 				Expected: []sql.Row{{types.NewOkResult(1)}},
 			},
 			{
 				Query:    "select * from t1 order by a",
-				Expected: []sql.Row{{2, 3}, {3, 4}, {4, 5}},
+				Expected: []sql.Row{{2, 3}, {3, 4}, {4, 5}, {5, 6}},
+			},
+		},
+	},
+	{
+		Name: "generated column with DEFAULT in VALUES clause (issue #9428)",
+		SetUpScript: []string{
+			"create table t (i int generated always as (1 + 1))",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query:    "insert into t values (default)",
+				Expected: []sql.Row{{types.NewOkResult(1)}},
+			},
+			{
+				Query:    "select * from t",
+				Expected: []sql.Row{{2}},
+			},
+			{
+				Query:    "insert into t values (default), (default)",
+				Expected: []sql.Row{{types.NewOkResult(2)}},
+			},
+			{
+				Query:    "select * from t order by i",
+				Expected: []sql.Row{{2}, {2}, {2}},
+			},
+			{
+				Query:       "insert into t values (5)",
+				ExpectedErr: sql.ErrGeneratedColumnValue,
 			},
 		},
 	},

sql/planbuilder/dml.go

@@ -76,10 +76,6 @@ func (b *Builder) buildInsert(inScope *scope, i *ast.Insert) (outScope *scope) {
 			schema := rt.Schema()
 			columns = make([]string, len(schema))
 			for i, col := range schema {
-				// Tables with any generated column must always supply a column list, so this is always an error
-				if col.Generated != nil {
-					b.handleErr(sql.ErrGeneratedColumnValue.New(col.Name, rt.Name()))
-				}
 				columns[i] = col.Name
 			}
 		}

sql/planbuilder/dml_validate.go

@@ -165,7 +165,12 @@ func validGeneratedColumnValue(idx int, source sql.Node) bool {
 				if _, ok := val.Unwrap().(*sql.ColumnDefaultValue); ok {
 					return true
 				}
+				if _, ok := val.Unwrap().(*expression.DefaultColumn); ok {
+					return true
+				}
 				return false
+			case *expression.DefaultColumn: // handle unwrapped DefaultColumn
+				return true
 			default:
 				return false
 			}