feat(spanner/spansql): support DEFAULT keyword

spanner/spannertest/README.md

@@ -23,6 +23,7 @@ by ascending esotericism:
 - more aggregation functions
 - SELECT HAVING
 - more literal types
+- DEFAULT
 - expressions that return null for generated columns
 - generated columns referencing other generated columns
 - checking dependencies on a generated column before deleting a column

spanner/spansql/parser.go

@@ -1528,7 +1528,7 @@ func (p *parser) parseColumnDef() (ColumnDef, *parseError) {
 
 	/*
 		column_def:
-			column_name {scalar_type | array_type} [NOT NULL] [AS ( expression ) STORED] [options_def]
+			column_name {scalar_type | array_type} [NOT NULL] [{DEFAULT ( expression ) | AS ( expression ) STORED}] [options_def]
 	*/
 
 	name, err := p.parseTableOrIndexOrColumnName()
@@ -1547,6 +1547,16 @@ func (p *parser) parseColumnDef() (ColumnDef, *parseError) {
 		cd.NotNull = true
 	}
 
+	if p.eat("DEFAULT", "(") {
+		cd.Default, err = p.parseExpr()
+		if err != nil {
+			return ColumnDef{}, err
+		}
+		if err := p.expect(")"); err != nil {
+			return ColumnDef{}, err
+		}
+	}
+
 	if p.eat("AS", "(") {
 		cd.Generated, err = p.parseExpr()
 		if err != nil {
@@ -1573,9 +1583,29 @@ func (p *parser) parseColumnDef() (ColumnDef, *parseError) {
 func (p *parser) parseColumnAlteration() (ColumnAlteration, *parseError) {
 	debugf("parseColumnAlteration: %v", p)
 	/*
-		{ data_type } [ NOT NULL ] | SET [ options_def ]
+		{
+			data_type [ NOT NULL ] [ DEFAULT ( expression ) ]
+			| SET  ( options_def )
+			| SET  DEFAULT ( expression )
+			| DROP DEFAULT
+		}
 	*/
 
+	if p.eat("SET", "DEFAULT", "(") {
+		d, err := p.parseExpr()
+		if err != nil {
+			return nil, err
+		}
+		if err := p.expect(")"); err != nil {
+			return nil, err
+		}
+		return SetDefault{Default: d}, nil
+	}
+
+	if p.eat("DROP", "DEFAULT") {
+		return DropDefault{}, nil
+	}
+
 	if p.eat("SET") {
 		co, err := p.parseColumnOptions()
 		if err != nil {
@@ -1594,6 +1624,16 @@ func (p *parser) parseColumnAlteration() (ColumnAlteration, *parseError) {
 		sct.NotNull = true
 	}
 
+	if p.eat("DEFAULT", "(") {
+		sct.Default, err = p.parseExpr()
+		if err != nil {
+			return nil, err
+		}
+		if err := p.expect(")"); err != nil {
+			return nil, err
+		}
+	}
+
 	return sct, nil
 }
 

spanner/spansql/parser_test.go

@@ -552,6 +552,16 @@ func TestParseDDL(t *testing.T) {
 		  shard_id  INT64 AS (MOD(FARM_FINGERPRINT(user_id), 19)) STORED,
 		) PRIMARY KEY(user_id);
 
+		-- Table has a column with a default value.
+		CREATE TABLE DefaultCol (
+			Name STRING(MAX) NOT NULL,
+			Age INT64 DEFAULT (0),
+		) PRIMARY KEY (Name);
+
+		ALTER TABLE DefaultCol ALTER COLUMN Age DROP DEFAULT;
+		ALTER TABLE DefaultCol ALTER COLUMN Age SET DEFAULT (0);
+		ALTER TABLE DefaultCol ALTER COLUMN Age STRING(MAX) DEFAULT ("0");
+
 		-- Trailing comment at end of file.
 		`, &DDL{Filename: "filename", List: []DDLStmt{
 			&CreateTable{
@@ -795,6 +805,49 @@ func TestParseDDL(t *testing.T) {
 				PrimaryKey: []KeyPart{{Column: "user_id"}},
 				Position:   line(66),
 			},
+
+			&CreateTable{
+				Name: "DefaultCol",
+				Columns: []ColumnDef{
+					{Name: "Name", Type: Type{Base: String, Len: MaxLen}, NotNull: true, Position: line(77)},
+					{
+						Name: "Age", Type: Type{Base: Int64},
+						Default:  IntegerLiteral(0),
+						Position: line(78),
+					},
+				},
+				PrimaryKey: []KeyPart{{Column: "Name"}},
+				Position:   line(76),
+			},
+			&AlterTable{
+				Name: "DefaultCol",
+				Alteration: AlterColumn{
+					Name:       "Age",
+					Alteration: DropDefault{},
+				},
+				Position: line(81),
+			},
+			&AlterTable{
+				Name: "DefaultCol",
+				Alteration: AlterColumn{
+					Name: "Age",
+					Alteration: SetDefault{
+						Default: IntegerLiteral(0),
+					},
+				},
+				Position: line(82),
+			},
+			&AlterTable{
+				Name: "DefaultCol",
+				Alteration: AlterColumn{
+					Name: "Age",
+					Alteration: SetColumnType{
+						Type:    Type{Base: String, Len: MaxLen},
+						Default: StringLiteral("0"),
+					},
+				},
+				Position: line(83),
+			},
 		}, Comments: []*Comment{
 			{Marker: "#", Start: line(2), End: line(2),
 				Text: []string{"This is a comment."}},
@@ -815,9 +868,10 @@ func TestParseDDL(t *testing.T) {
 
 			{Marker: "--", Isolated: true, Start: line(43), End: line(43), Text: []string{"Table with generated column."}},
 			{Marker: "--", Isolated: true, Start: line(49), End: line(49), Text: []string{"Table with row deletion policy."}},
+			{Marker: "--", Isolated: true, Start: line(75), End: line(75), Text: []string{"Table has a column with a default value."}},
 
 			// Comment after everything else.
-			{Marker: "--", Isolated: true, Start: line(75), End: line(75), Text: []string{"Trailing comment at end of file."}},
+			{Marker: "--", Isolated: true, Start: line(85), End: line(85), Text: []string{"Trailing comment at end of file."}},
 		}}},
 		// No trailing comma:
 		{`ALTER TABLE T ADD COLUMN C2 INT64`, &DDL{Filename: "filename", List: []DDLStmt{

spanner/spansql/sql.go

@@ -162,6 +162,9 @@ func (sct SetColumnType) SQL() string {
 	if sct.NotNull {
 		str += " NOT NULL"
 	}
+	if sct.Default != nil {
+		str += " DEFAULT (" + sct.Default.SQL() + ")"
+	}
 	return str
 }
 
@@ -170,6 +173,14 @@ func (sco SetColumnOptions) SQL() string {
 	return "SET " + sco.Options.SQL()
 }
 
+func (sd SetDefault) SQL() string {
+	return "SET DEFAULT (" + sd.Default.SQL() + ")"
+}
+
+func (dp DropDefault) SQL() string {
+	return "DROP DEFAULT"
+}
+
 func (co ColumnOptions) SQL() string {
 	str := "OPTIONS ("
 	if co.AllowCommitTimestamp != nil {
@@ -254,6 +265,9 @@ func (cd ColumnDef) SQL() string {
 	if cd.NotNull {
 		str += " NOT NULL"
 	}
+	if cd.Default != nil {
+		str += " DEFAULT (" + cd.Default.SQL() + ")"
+	}
 	if cd.Generated != nil {
 		str += " AS (" + cd.Generated.SQL() + ") STORED"
 	}

spanner/spansql/sql_test.go

@@ -85,6 +85,7 @@ func TestSQL(t *testing.T) {
 					{Name: "Cl", Type: Type{Base: Timestamp}, Options: ColumnOptions{AllowCommitTimestamp: boolAddr(false)}, Position: line(13)},
 					{Name: "Cm", Type: Type{Base: Int64}, Generated: Func{Name: "CHAR_LENGTH", Args: []Expr{ID("Ce")}}, Position: line(14)},
 					{Name: "Cn", Type: Type{Base: JSON}, Position: line(15)},
+					{Name: "Co", Type: Type{Base: Int64}, Default: IntegerLiteral(1), Position: line(16)},
 				},
 				PrimaryKey: []KeyPart{
 					{Column: "Ca"},
@@ -107,6 +108,7 @@ func TestSQL(t *testing.T) {
   Cl TIMESTAMP OPTIONS (allow_commit_timestamp = null),
   Cm INT64 AS (CHAR_LENGTH(Ce)) STORED,
   Cn JSON,
+  Co INT64 DEFAULT (1),
 ) PRIMARY KEY(Ca, Cb DESC)`,
 			reparseDDL,
 		},
@@ -266,6 +268,22 @@ func TestSQL(t *testing.T) {
 			"ALTER TABLE Ta ALTER COLUMN Cg STRING(MAX)",
 			reparseDDL,
 		},
+		{
+			&AlterTable{
+				Name: "Ta",
+				Alteration: AlterColumn{
+					Name: "Ch",
+					Alteration: SetColumnType{
+						Type:    Type{Base: String, Len: MaxLen},
+						NotNull: true,
+						Default: StringLiteral("1"),
+					},
+				},
+				Position: line(1),
+			},
+			"ALTER TABLE Ta ALTER COLUMN Ch STRING(MAX) NOT NULL DEFAULT (\"1\")",
+			reparseDDL,
+		},
 		{
 			&AlterTable{
 				Name: "Ta",
@@ -282,6 +300,32 @@ func TestSQL(t *testing.T) {
 			"ALTER TABLE Ta ALTER COLUMN Ci SET OPTIONS (allow_commit_timestamp = null)",
 			reparseDDL,
 		},
+		{
+			&AlterTable{
+				Name: "Ta",
+				Alteration: AlterColumn{
+					Name: "Cj",
+					Alteration: SetDefault{
+						Default: StringLiteral("1"),
+					},
+				},
+				Position: line(1),
+			},
+			"ALTER TABLE Ta ALTER COLUMN Cj SET DEFAULT (\"1\")",
+			reparseDDL,
+		},
+		{
+			&AlterTable{
+				Name: "Ta",
+				Alteration: AlterColumn{
+					Name:       "Ck",
+					Alteration: DropDefault{},
+				},
+				Position: line(1),
+			},
+			"ALTER TABLE Ta ALTER COLUMN Ck DROP DEFAULT",
+			reparseDDL,
+		},
 		{
 			&AlterTable{
 				Name:       "WithRowDeletionPolicy",

spanner/spansql/types.go

@@ -235,14 +235,23 @@ type ColumnAlteration interface {
 
 func (SetColumnType) isColumnAlteration()    {}
 func (SetColumnOptions) isColumnAlteration() {}
+func (SetDefault) isColumnAlteration()       {}
+func (DropDefault) isColumnAlteration()      {}
 
 type SetColumnType struct {
 	Type    Type
 	NotNull bool
+	Default Expr
 }
 
 type SetColumnOptions struct{ Options ColumnOptions }
 
+type SetDefault struct {
+	Default Expr
+}
+
+type DropDefault struct{}
+
 type OnDelete int
 
 const (
@@ -320,6 +329,7 @@ type ColumnDef struct {
 	Type    Type
 	NotNull bool
 
+	Default   Expr // set if this column has a default value
 	Generated Expr // set of this is a generated column
 
 	Options ColumnOptions