meta

ctx := context.TODO()
db, err := ydb.Open(ctx, "grpc://localhost:2136/local")
if err != nil {
	log.Fatal(err)
}
defer db.Close(ctx) // cleanup resources
var (
	query              = `SELECT 42 as id, "my string" as myStr`
	id                 int32  // required value
	myStr              string // optional value
	totalConsumedUnits uint64
)
err = db.Table().Do( // Do retry operation on errors with best effort
	meta.WithTrailerCallback(ctx, func(md metadata.MD) {
		totalConsumedUnits += meta.ConsumedUnits(md)
	}),
	func(ctx context.Context, s table.Session) (err error) { // retry operation
		_, res, err := s.Execute(ctx, table.DefaultTxControl(), query, nil)
		if err != nil {
			return err // for auto-retry with driver
		}
		defer res.Close()                                // cleanup resources
		if err = res.NextResultSetErr(ctx); err != nil { // check single result set and switch to it
			return err // for auto-retry with driver
		}
		for res.NextRow() { // iterate over rows
			err = res.ScanNamed(
				named.Required("id", &id),
				named.OptionalWithDefault("myStr", &myStr),
			)
			if err != nil {
				return err // generally scan error not retryable, return it for driver check error
			}
			log.Printf("id=%v, myStr='%s'\n", id, myStr)
		}

		return res.Err() // return finally result error for auto-retry with driver
	},
	table.WithIdempotent(),
)
if err != nil {
	log.Printf("unexpected error: %v", err)
}
log.Println("total consumed units:", totalConsumedUnits)