tx.go
func TraceDatastore(ctx context.Context, table, operation, sql, rollupName string) *Trace {
	return trace(ctx, rollupName, func(tx Tx) error {
		return tx.StartDatastore(table, operation, sql, rollupName)
	})
}
func TraceDatastore(ctx context.Context, table, operation, sql, rollupName string) *Trace {
	return trace(ctx, rollupName, func(tx Tx) error {
		return tx.StartDatastore(table, operation, sql, rollupName)
	})
}
// TraceDatastore adds a datastore segment to the newrelic transaction, if one exists in the context.