DO $$
BEGIN
  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = '{{.SchemaName}}'
      AND table_name = '{{.TableName}}'
      AND column_name = '{{.ColumnName}}'
  ) THEN
    ALTER TABLE {{quote_ident .SchemaName}}.{{quote_ident .TableName}} ADD COLUMN {{.ColumnDefinition}};
  END IF;
END;
$$;