feat(spanner/spansql): support for parsing generated columns

spanner/spannertest/README.md

@@ -21,15 +21,16 @@ by ascending esotericism:
 - more aggregation functions
 - SELECT HAVING
 - case insensitivity
-- multiple joins
 - alternate literal types (esp. strings)
-- STRUCT types
-- transaction simulation
+- generated columns
 - expression type casting, coercion
+- multiple joins
 - subselects
+- transaction simulation
 - FOREIGN KEY and CHECK constraints
 - INSERT DML statements
 - set operations (UNION, INTERSECT, EXCEPT)
+- STRUCT types
 - partition support
 - conditional expressions
 - table sampling (implementation)

spanner/spansql/keywords.go

@@ -143,5 +143,8 @@ var funcs = map[string]bool{
 	// Hash functions.
 	"SHA1": true,
 
+	// String functions.
+	"CHAR_LENGTH": true,
+
 	// TODO: many more
 }

spanner/spansql/parser.go

@@ -1373,7 +1373,7 @@ func (p *parser) parseColumnDef() (ColumnDef, *parseError) {
 
 	/*
 		column_def:
-			column_name {scalar_type | array_type} [NOT NULL] [options_def]
+			column_name {scalar_type | array_type} [NOT NULL] [AS ( expression ) STORED] [options_def]
 	*/
 
 	name, err := p.parseTableOrIndexOrColumnName()
@@ -1392,6 +1392,19 @@ func (p *parser) parseColumnDef() (ColumnDef, *parseError) {
 		cd.NotNull = true
 	}
 
+	if p.eat("AS", "(") {
+		cd.Generated, err = p.parseExpr()
+		if err != nil {
+			return ColumnDef{}, err
+		}
+		if err := p.expect(")"); err != nil {
+			return ColumnDef{}, err
+		}
+		if err := p.expect("STORED"); err != nil {
+			return ColumnDef{}, err
+		}
+	}
+
 	if p.sniff("OPTIONS") {
 		cd.Options, err = p.parseColumnOptions()
 		if err != nil {

spanner/spansql/parser_test.go

@@ -379,6 +379,12 @@ func TestParseDDL(t *testing.T) {
 			Names ARRAY<STRING(MAX)>,
 		) PRIMARY KEY (Dummy);
 
+		-- Table with generated column.
+		CREATE TABLE GenCol (
+			Name STRING(MAX) NOT NULL,
+			NameLen INT64 AS (CHAR_LENGTH(Name)) STORED,
+		) PRIMARY KEY (Name);
+
 		-- Trailing comment at end of file.
 		`, &DDL{Filename: "filename", List: []DDLStmt{
 			&CreateTable{
@@ -517,6 +523,19 @@ func TestParseDDL(t *testing.T) {
 				PrimaryKey: []KeyPart{{Column: "Dummy"}},
 				Position:   line(35),
 			},
+			&CreateTable{
+				Name: "GenCol",
+				Columns: []ColumnDef{
+					{Name: "Name", Type: Type{Base: String, Len: MaxLen}, NotNull: true, Position: line(45)},
+					{
+						Name: "NameLen", Type: Type{Base: Int64},
+						Generated: Func{Name: "CHAR_LENGTH", Args: []Expr{ID("Name")}},
+						Position:  line(46),
+					},
+				},
+				PrimaryKey: []KeyPart{{Column: "Name"}},
+				Position:   line(44),
+			},
 		}, Comments: []*Comment{
 			{Marker: "#", Start: line(2), End: line(2),
 				Text: []string{"This is a comment."}},
@@ -535,8 +554,10 @@ func TestParseDDL(t *testing.T) {
 			{Marker: "--", Start: line(37), End: line(37), Text: []string{"comment on ids"}},
 			{Marker: "--", Isolated: true, Start: line(38), End: line(38), Text: []string{"leading multi comment immediately after inline comment"}},
 
+			{Marker: "--", Isolated: true, Start: line(43), End: line(43), Text: []string{"Table with generated column."}},
+
 			// Comment after everything else.
-			{Marker: "--", Isolated: true, Start: line(43), End: line(43), Text: []string{"Trailing comment at end of file."}},
+			{Marker: "--", Isolated: true, Start: line(49), End: line(49), 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

@@ -180,6 +180,9 @@ func (cd ColumnDef) SQL() string {
 	if cd.NotNull {
 		str += " NOT NULL"
 	}
+	if cd.Generated != nil {
+		str += " AS (" + cd.Generated.SQL() + ") STORED"
+	}
 	if cd.Options != (ColumnOptions{}) {
 		str += " " + cd.Options.SQL()
 	}

spanner/spansql/sql_test.go

@@ -75,6 +75,7 @@ func TestSQL(t *testing.T) {
 					{Name: "Cj", Type: Type{Array: true, Base: Int64}, Position: line(11)},
 					{Name: "Ck", Type: Type{Array: true, Base: String, Len: MaxLen}, Position: line(12)},
 					{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)},
 				},
 				PrimaryKey: []KeyPart{
 					{Column: "Ca"},
@@ -95,6 +96,7 @@ func TestSQL(t *testing.T) {
   Cj ARRAY<INT64>,
   Ck ARRAY<STRING(MAX)>,
   Cl TIMESTAMP OPTIONS (allow_commit_timestamp = null),
+  Cm INT64 AS (CHAR_LENGTH(Ce)) STORED,
 ) PRIMARY KEY(Ca, Cb DESC)`,
 			reparseDDL,
 		},

spanner/spansql/types.go

@@ -244,6 +244,8 @@ type ColumnDef struct {
 	Type    Type
 	NotNull bool
 
+	Generated Expr // set of this is a generated column
+
 	Options ColumnOptions
 
 	Position Position // position of the column name