dialect/sql/schema: skip parsing expression default for postgres

Fixed https://github.com/ent/ent/issues/1962

dialect/sql/schema/postgres.go

@@ -295,7 +295,7 @@ func (d *Postgres) scanColumn(c *Column, rows *sql.Rows) error {
 		c.SchemaType = map[string]string{dialect.Postgres: udt.String}
 	}
 	switch {
-	case !defaults.Valid || c.Type == field.TypeTime || seqfunc(defaults.String):
+	case !defaults.Valid || c.Type == field.TypeTime || callExpr(defaults.String):
 		return nil
 	case strings.Contains(defaults.String, "::"):
 		parts := strings.Split(defaults.String, "::")
@@ -374,13 +374,32 @@ func (d *Postgres) addColumn(c *Column) *sql.ColumnBuilder {
 		b.Attr("GENERATED BY DEFAULT AS IDENTITY")
 	}
 	c.nullable(b)
-	c.defaultValue(b)
+	d.writeDefault(b, c)
 	if c.Collation != "" {
 		b.Attr("COLLATE " + strconv.Quote(c.Collation))
 	}
 	return b
 }
 
+// writeDefault writes the `DEFAULT` clause to column builder
+// if exists and supported by the driver.
+func (d *Postgres) writeDefault(b *sql.ColumnBuilder, c *Column) {
+	if c.Default == nil || !c.supportDefault() {
+		return
+	}
+	attr := fmt.Sprint(c.Default)
+	switch v := c.Default.(type) {
+	case bool:
+		attr = strconv.FormatBool(v)
+	case string:
+		if t := c.Type; t != field.TypeUUID && t != field.TypeTime && !t.Numeric() {
+			// Escape single quote by replacing each with 2.
+			attr = fmt.Sprintf("'%s'", strings.ReplaceAll(v, "'", "''"))
+		}
+	}
+	b.Attr("DEFAULT " + attr)
+}
+
 // alterColumn returns list of ColumnBuilder for applying in order to alter a column.
 func (d *Postgres) alterColumn(c *Column) (ops []*sql.ColumnBuilder) {
 	b := sql.Dialect(dialect.Postgres)
@@ -522,14 +541,25 @@ func (d *Postgres) needsConversion(old, new *Column) bool {
 	return oldT != newT && (oldT != "ARRAY" || !arrayType(newT))
 }
 
-// seqfunc reports if the given string is a sequence function.
-func seqfunc(defaults string) bool {
-	for _, fn := range [...]string{"currval", "lastval", "setval", "nextval"} {
-		if strings.HasPrefix(defaults, fn+"(") && strings.HasSuffix(defaults, ")") {
-			return true
+// callExpr reports if the given string ~looks like a function call expression.
+func callExpr(s string) bool {
+	if parts := strings.Split(s, "::"); !strings.HasSuffix(s, ")") && strings.HasSuffix(parts[0], ")") {
+		s = parts[0]
+	}
+	i, j := strings.IndexByte(s, '('), strings.LastIndexByte(s, ')')
+	if i == -1 || i > j || j != len(s)-1 {
+		return false
+	}
+	for i, r := range s[:i] {
+		if !isAlpha(r, i > 0) {
+			return false
 		}
 	}
-	return false
+	return true
+}
+
+func isAlpha(r rune, digit bool) bool {
+	return 'a' <= r && r <= 'z' || 'A' <= r && r <= 'Z' || r == '_' || digit && '0' <= r && r <= '9'
 }
 
 // arrayType reports if the given string is an array type (e.g. int[], text[2]).

dialect/sql/schema/postgres_test.go

@@ -59,6 +59,7 @@ func TestPostgres_Create(t *testing.T) {
 					},
 					Columns: []*Column{
 						{Name: "id", Type: field.TypeUUID, Default: "uuid_generate_v4()"},
+						{Name: "block_size", Type: field.TypeInt, Default: "current_setting('block_size')::bigint"},
 						{Name: "name", Type: field.TypeString, Nullable: true, Collation: "he_IL"},
 						{Name: "age", Type: field.TypeInt},
 						{Name: "doc", Type: field.TypeJSON, Nullable: true},
@@ -77,7 +78,7 @@ func TestPostgres_Create(t *testing.T) {
 			before: func(mock pgMock) {
 				mock.start("120000")
 				mock.tableExists("users", false)
-				mock.ExpectExec(escape(`CREATE TABLE IF NOT EXISTS "users"("id" uuid NOT NULL DEFAULT uuid_generate_v4(), "name" varchar NULL COLLATE "he_IL", "age" bigint NOT NULL, "doc" jsonb NULL, "enums" varchar NOT NULL DEFAULT 'a', "price" numeric(5,2) NOT NULL, "strings" text[] NULL, PRIMARY KEY("id"), CHECK (price > 0), CONSTRAINT "valid_name" CHECK (name <> ''))`)).
+				mock.ExpectExec(escape(`CREATE TABLE IF NOT EXISTS "users"("id" uuid NOT NULL DEFAULT uuid_generate_v4(), "block_size" bigint NOT NULL DEFAULT current_setting('block_size')::bigint, "name" varchar NULL COLLATE "he_IL", "age" bigint NOT NULL, "doc" jsonb NULL, "enums" varchar NOT NULL DEFAULT 'a', "price" numeric(5,2) NOT NULL, "strings" text[] NULL, PRIMARY KEY("id"), CHECK (price > 0), CONSTRAINT "valid_name" CHECK (name <> ''))`)).
 					WillReturnResult(sqlmock.NewResult(0, 1))
 				mock.ExpectCommit()
 			},
@@ -184,12 +185,13 @@ func TestPostgres_Create(t *testing.T) {
 			},
 		},
 		{
-			name: "scan table with default set to serial",
+			name: "scan table with default",
 			tables: []*Table{
 				{
 					Name: "users",
 					Columns: []*Column{
 						{Name: "id", Type: field.TypeInt, Increment: true},
+						{Name: "block_size", Type: field.TypeInt, Default: "current_setting('block_size')::bigint"},
 					},
 					PrimaryKey: []*Column{
 						{Name: "id", Type: field.TypeInt, Increment: true},
@@ -202,7 +204,8 @@ func TestPostgres_Create(t *testing.T) {
 				mock.ExpectQuery(escape(`SELECT "column_name", "data_type", "is_nullable", "column_default", "udt_name", "numeric_precision", "numeric_scale" FROM "information_schema"."columns" WHERE "table_schema" = CURRENT_SCHEMA() AND "table_name" = $1`)).
 					WithArgs("users").
 					WillReturnRows(sqlmock.NewRows([]string{"column_name", "data_type", "is_nullable", "column_default", "udt_name", "numeric_precision", "numeric_scale"}).
-						AddRow("id", "bigint", "NO", "nextval('users_colname_seq'::regclass)", "int4", nil, nil))
+						AddRow("id", "bigint", "NO", "nextval('users_colname_seq'::regclass)", "int4", nil, nil).
+						AddRow("block_size", "bigint", "NO", "current_setting('block_size')::bigint", "int4", nil, nil))
 				mock.ExpectQuery(escape(fmt.Sprintf(indexesQuery, "CURRENT_SCHEMA()", "users"))).
 					WillReturnRows(sqlmock.NewRows([]string{"index_name", "column_name", "primary", "unique", "seq_in_index"}).
 						AddRow("users_pkey", "id", "t", "t", 0))