ent/schema: fix indexes in mysql versions <= 5.6

Summary: move property type uniqueness enforment to ent schema

Reviewed By: alexsn

Differential Revision: D16767355

fbshipit-source-id: db6ba4853a8816fd5f6299a34c0b780028d75da1

dialect/sql/schema/migrate.go

@@ -103,6 +103,7 @@ func (m *Migrate) Create(ctx context.Context, tables ...*Table) error {
 
 func (m *Migrate) create(ctx context.Context, tx dialect.Tx, tables ...*Table) error {
 	for _, t := range tables {
+		t.linkColumns()
 		switch exist, err := m.tableExist(ctx, tx, t.Name); {
 		case err != nil:
 			return err

dialect/sql/schema/mysql.go

@@ -55,7 +55,7 @@ func (d *MySQL) table(ctx context.Context, tx dialect.Tx, name string) (*Table,
 	}
 	// call `Close` in cases of failures (`Close` is idempotent).
 	defer rows.Close()
-	t := &Table{Name: name}
+	t := NewTable(name)
 	for rows.Next() {
 		c := &Column{}
 		if err := c.ScanMySQL(rows); err != nil {
@@ -64,7 +64,7 @@ func (d *MySQL) table(ctx context.Context, tx dialect.Tx, name string) (*Table,
 		if c.PrimaryKey() {
 			t.PrimaryKey = append(t.PrimaryKey, c)
 		}
-		t.Columns = append(t.Columns, c)
+		t.AddColumn(c)
 	}
 	if err := rows.Close(); err != nil {
 		return nil, fmt.Errorf("mysql: closing rows %v", err)
@@ -73,7 +73,10 @@ func (d *MySQL) table(ctx context.Context, tx dialect.Tx, name string) (*Table,
 	if err != nil {
 		return nil, err
 	}
-	t.Indexes = indexes
+	// add and link indexes to table columns.
+	for _, idx := range indexes {
+		t.AddIndex(idx.Name, idx.Unique, idx.columns)
+	}
 	return t, nil
 }
 

dialect/sql/schema/schema.go

@@ -62,12 +62,22 @@ func (t *Table) AddIndex(name string, unique bool, columns []string) *Table {
 		c, ok := t.columns[name]
 		if ok {
 			idx.Columns[i] = c
+			c.indexes = append(c.indexes, idx)
 		}
 	}
 	t.Indexes = append(t.Indexes, idx)
 	return t
 }
 
+// linkColumns links the table columns to their indexes for later referencing.
+func (t *Table) linkColumns() {
+	for _, idx := range t.Indexes {
+		for _, c := range idx.Columns {
+			c.indexes.append(idx)
+		}
+	}
+}
+
 // MySQL returns the MySQL DSL query for table creation.
 func (t *Table) MySQL(version string) *sql.TableBuilder {
 	b := sql.CreateTable(t.Name).IfNotExists()
@@ -148,6 +158,7 @@ type Column struct {
 	Default   string     // default value.
 	Charset   string     // column character set.
 	Collation string     // column collation.
+	indexes   Indexes    // linked indexes.
 }
 
 // UniqueKey returns boolean indicates if this column is a unique key.
@@ -372,18 +383,23 @@ func (c *Column) nullable(b *sql.ColumnBuilder) {
 	}
 }
 
-// defaultSize returns the default size for MySQL varchar
-// type based on column size, charset and table indexes.
+// defaultSize returns the default size for MySQL varchar type based
+// on column size, charset and table indexes, in order to avoid index
+// prefix key limit (767).
 func (c *Column) defaultSize(version string) int {
+	size := DefaultStringLen
 	parts := strings.Split(version, ".")
-	// non-unique or invalid version.
-	if !c.Unique || len(parts) == 1 || parts[0] == "" || parts[1] == "" {
-		return DefaultStringLen
+	switch {
+	// invalid version.
+	case len(parts) == 1 || parts[0] == "" || parts[1] == "":
+	// version is > 5.6.*.
+	case parts[0] > "5" || parts[1] > "6":
+	// non-unique, or not part of any index (reaching the error 1071).
+	case !c.Unique && len(c.indexes) == 0:
+	default:
+		size = 191
 	}
-	if major, minor := parts[0], parts[1]; major > "5" || minor > "6" {
-		return DefaultStringLen
-	}
-	return 191
+	return size
 }
 
 // ForeignKey definition for creation.