ent/migrate: add writedriver for dumping sql exec commands

Reviewed By: alexsn

Differential Revision: D17200893

fbshipit-source-id: 09ec631b5a52d617d0ee97bda81c52f67486889e

dialect/sql/schema/writer.go

@@ -0,0 +1,44 @@
+package schema
+
+import (
+	"context"
+	"io"
+	"strings"
+
+	"github.com/facebookincubator/ent/dialect"
+)
+
+// WriterDriver is a driver that writes all driver exec operations to its writer.
+type WriteDriver struct {
+	dialect.Driver // underlying driver.
+	io.Writer      // target for exec statements.
+}
+
+// Exec writes its query and calls the underlying driver Exec method.
+func (w *WriteDriver) Exec(_ context.Context, query string, _, _ interface{}) error {
+	if !strings.HasSuffix(query, ";") {
+		query += ";"
+	}
+	_, err := io.WriteString(w, query+"\n")
+	return err
+}
+
+// Tx writes the transaction start.
+func (w *WriteDriver) Tx(context.Context) (dialect.Tx, error) {
+	if _, err := io.WriteString(w, "BEGIN;\n"); err != nil {
+		return nil, err
+	}
+	return w, nil
+}
+
+// Commit writes the transaction commit.
+func (w *WriteDriver) Commit() error {
+	_, err := io.WriteString(w, "COMMIT;\n")
+	return err
+}
+
+// Rollback writes the transaction rollback.
+func (w *WriteDriver) Rollback() error {
+	_, err := io.WriteString(w, "ROLLBACK;\n")
+	return err
+}