dialect/sql/schema: initial work for incremental migration

This is a WIP PR and should be ignored this moment.
It's based on PR #221 created by Erik Hollensbe (He should
get his credit for his work before we land this).

.golangci.yml

@@ -57,9 +57,9 @@ issues:
       text: "SQL string concatenation"
       linters:
         - gosec
-    - path: dialect/sql/schema/migrate.go
-      text: "weak cryptographic primitive"
+    - path: dialect/sql/schema
       linters:
+        - dupl
         - gosec
     - path: entc/load/load.go
       text: "packages.LoadSyntax is deprecated"

dialect/sql/builder.go

@@ -25,10 +25,11 @@ type Querier interface {
 // ColumnBuilder is a builder for column definition in table creation.
 type ColumnBuilder struct {
 	Builder
-	typ    string // column type.
-	name   string // column name.
-	attr   string // extra attributes.
-	modify bool   // modify existing.
+	typ    string             // column type.
+	name   string             // column name.
+	attr   string             // extra attributes.
+	modify bool               // modify existing.
+	fk     *ForeignKeyBuilder // foreign-key constraint.
 }
 
 // Column returns a new ColumnBuilder with the given name.
@@ -52,6 +53,12 @@ func (c *ColumnBuilder) Attr(attr string) *ColumnBuilder {
 	return c
 }
 
+// Constraint adds the CONSTRAINT clause to the ADD COLUMN statement in SQLite.
+func (c *ColumnBuilder) Constraint(fk *ForeignKeyBuilder) *ColumnBuilder {
+	c.fk = fk
+	return c
+}
+
 // Query returns query representation of a Column.
 func (c *ColumnBuilder) Query() (string, []interface{}) {
 	c.Ident(c.name)
@@ -64,6 +71,13 @@ func (c *ColumnBuilder) Query() (string, []interface{}) {
 	if c.attr != "" {
 		c.Pad().WriteString(c.attr)
 	}
+	if c.fk != nil {
+		c.WriteString(" CONSTRAINT " + c.fk.symbol)
+		c.Pad().Join(c.fk.ref)
+		for _, action := range c.fk.actions {
+			c.Pad().WriteString(action)
+		}
+	}
 	return c.String(), c.args
 }
 

dialect/sql/builder_test.go

@@ -1164,6 +1164,20 @@ func TestBuilder(t *testing.T) {
 			input:     DropIndex("name_index").Table("users"),
 			wantQuery: "DROP INDEX `name_index` ON `users`",
 		},
+		{
+			input: Select().
+				From(Table("pragma_table_info('t1')").Unquote()).
+				OrderBy("pk"),
+			wantQuery: "SELECT * FROM pragma_table_info('t1') ORDER BY `pk`",
+		},
+		{
+			input: AlterTable("users").
+				AddColumn(Column("spouse").Type("integer").
+					Constraint(ForeignKey("user_spouse").
+						Reference(Reference().Table("users").Columns("id")).
+						OnDelete("SET NULL"))),
+			wantQuery: "ALTER TABLE `users` ADD COLUMN `spouse` integer CONSTRAINT user_spouse REFERENCES `users`(`id`) ON DELETE SET NULL",
+		},
 	}
 	for i, tt := range tests {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {

dialect/sql/schema/migrate.go

@@ -209,21 +209,14 @@ func (m *Migrate) apply(ctx context.Context, tx dialect.Tx, table string, change
 			}
 		}
 	}
-	b := sql.Dialect(m.Dialect()).AlterTable(table)
-	for _, c := range change.column.add {
-		b.AddColumn(m.addColumn(c))
-	}
-	for _, c := range change.column.modify {
-		b.ModifyColumns(m.alterColumn(c)...)
-	}
+	var drop []*Column
 	if m.dropColumns {
-		for _, c := range change.column.drop {
-			b.DropColumn(sql.Dialect(m.Dialect()).Column(c.Name))
-		}
+		drop = change.column.drop
 	}
+	queries := m.alterColumns(table, change.column.add, change.column.modify, drop)
 	// If there's actual action to execute on ALTER TABLE.
-	if len(b.Queries) != 0 {
-		query, args := b.Query()
+	for i := range queries {
+		query, args := queries[i].Query()
 		if err := tx.Exec(ctx, query, args, nil); err != nil {
 			return fmt.Errorf("alter table %q: %v", table, err)
 		}
@@ -532,6 +525,9 @@ func (m *Migrate) setupTable(t *Table) {
 	}
 	for _, fk := range t.ForeignKeys {
 		fk.Symbol = m.symbol(fk.Symbol)
+		for i := range fk.Columns {
+			fk.Columns[i].foreign = fk
+		}
 	}
 }
 
@@ -590,9 +586,8 @@ type sqlDialect interface {
 	// table, column and index builder per dialect.
 	cType(*Column) string
 	tBuilder(*Table) *sql.TableBuilder
-	addColumn(*Column) *sql.ColumnBuilder
-	alterColumn(*Column) []*sql.ColumnBuilder
 	addIndex(*Index, string) *sql.IndexBuilder
+	alterColumns(table string, add, modify, drop []*Column) sql.Queries
 }
 
 type preparer interface {

dialect/sql/schema/mysql.go

@@ -243,11 +243,6 @@ func (d *MySQL) addColumn(c *Column) *sql.ColumnBuilder {
 	return b
 }
 
-// alterColumn returns the DSL query for modifying the given column.
-func (d *MySQL) alterColumn(c *Column) []*sql.ColumnBuilder {
-	return []*sql.ColumnBuilder{d.addColumn(c)}
-}
-
 // addIndex returns the querying for adding an index to MySQL.
 func (d *MySQL) addIndex(i *Index, table string) *sql.IndexBuilder {
 	return i.Builder(table)
@@ -465,6 +460,24 @@ func (d *MySQL) tableSchema() sql.Querier {
 	return sql.Raw("(SELECT DATABASE())")
 }
 
+// alterColumns returns the queries for applying the columns change-set.
+func (d *MySQL) alterColumns(table string, add, modify, drop []*Column) sql.Queries {
+	b := sql.Dialect(dialect.MySQL).AlterTable(table)
+	for _, c := range add {
+		b.AddColumn(d.addColumn(c))
+	}
+	for _, c := range modify {
+		b.ModifyColumn(d.addColumn(c))
+	}
+	for _, c := range drop {
+		b.DropColumn(sql.Dialect(dialect.MySQL).Column(c.Name))
+	}
+	if len(b.Queries) == 0 {
+		return nil
+	}
+	return sql.Queries{b}
+}
+
 // parseColumn returns column parts, size and signedness by mysql type
 func parseColumn(typ string) (parts []string, size int64, unsigned bool, err error) {
 	switch parts = strings.FieldsFunc(typ, func(r rune) bool {

dialect/sql/schema/mysql_test.go

@@ -388,7 +388,7 @@ func TestMySQL_Create(t *testing.T) {
 			},
 		},
 		{
-			name: "add bool column with default value to table",
+			name: "add bool column with default value",
 			tables: []*Table{
 				{
 					Name: "users",
@@ -420,7 +420,7 @@ func TestMySQL_Create(t *testing.T) {
 			},
 		},
 		{
-			name: "add string column with default value to table",
+			name: "add string column with default value",
 			tables: []*Table{
 				{
 					Name: "users",
@@ -452,7 +452,7 @@ func TestMySQL_Create(t *testing.T) {
 			},
 		},
 		{
-			name: "add column with unsupported default value to table",
+			name: "add column with unsupported default value",
 			tables: []*Table{
 				{
 					Name: "users",
@@ -484,7 +484,7 @@ func TestMySQL_Create(t *testing.T) {
 			},
 		},
 		{
-			name: "drop column to table",
+			name: "drop columns",
 			tables: []*Table{
 				{
 					Name: "users",

dialect/sql/schema/postgres.go

@@ -382,3 +382,21 @@ func (d *Postgres) renameIndex(t *Table, old, new *Index) sql.Querier {
 func (d *Postgres) tableSchema() sql.Querier {
 	return sql.Raw("(CURRENT_SCHEMA())")
 }
+
+// alterColumns returns the queries for applying the columns change-set.
+func (d *Postgres) alterColumns(table string, add, modify, drop []*Column) sql.Queries {
+	b := sql.Dialect(dialect.Postgres).AlterTable(table)
+	for _, c := range add {
+		b.AddColumn(d.addColumn(c))
+	}
+	for _, c := range modify {
+		b.ModifyColumns(d.alterColumn(c)...)
+	}
+	for _, c := range drop {
+		b.DropColumn(sql.Dialect(dialect.Postgres).Column(c.Name))
+	}
+	if len(b.Queries) == 0 {
+		return nil
+	}
+	return sql.Queries{b}
+}

dialect/sql/schema/schema.go

@@ -98,7 +98,6 @@ func (t *Table) column(name string) (*Column, bool) {
 }
 
 // index returns a table index by its name.
-// faster than map lookup for most cases.
 func (t *Table) index(name string) (*Index, bool) {
 	for _, idx := range t.Indexes {
 		if idx.Name == name {
@@ -150,6 +149,7 @@ type Column struct {
 	Default   interface{} // default value.
 	Enums     []string    // enum values.
 	indexes   Indexes     // linked indexes.
+	foreign   *ForeignKey // linked foreign-key.
 }
 
 // UniqueKey returns boolean indicates if this column is a unique key.
@@ -186,7 +186,7 @@ func (c Column) FloatType() bool { return c.Type == field.TypeFloat32 || c.Type
 // ScanDefault scans the default value string to its interface type.
 func (c *Column) ScanDefault(value string) (err error) {
 	switch {
-	case value == Null: // ignore.
+	case strings.ToUpper(value) == Null: // ignore.
 	case c.IntType():
 		v := &sql.NullInt64{}
 		if err := v.Scan(value); err != nil {