databasegotarantool

How to get only one field from Tarantool Database by index with go-tarantool

Is there way to get only one field from tarantool db, not whole table?

Currently my request looks like:

result := Result{}
err := tConn.Do(tarantool.NewSelectRequest(spaceName).
    Context(ctx).
    Index("primary").
    Key(tarantool.IntKey{I: id}).
    Limit(1),
).GetTyped(&result)

but want something like this:

result := Result{}
err := tConn.Do(tarantool.NewSelectRequest(spaceName).
    Context(ctx).
    Index("primary").
    Key(tarantool.IntKey{I: id}).
    QueryFieldName("field_name").
    Limit(1),
).GetTyped(&result)

Is it even possible?

I tried to use sql syntax with go-tarantool. But it's going to be deprecated. And i doubt that perfomance wise, and that it's really getting only one field under the hood. Didn't find anything in official godoc nor googling didn't help me.

Solution

  • There is no proper API in select. If you want to fetch a single tuple field from the Tarantool instance (and not "fetch all, extract one on the client"), you should create a Lua store procedure and Call it or send the procedure code in Eval request. Lua code will be something like

    return box.space['my_space'].index['my_index']:select({key})[my_field]

    You can pass arguments into these procedures as well.