On Aug 9, 10:26 pm, Michael Lang <[email protected]> wrote:
> Would it be possible to enhance the Dataset#get so that an array can be
> passed and get back an array?
>
> i.e.
>
> charges, payments, balance = DB[:billing_headers].filter(:billing =>
> 5).get(:charges, :payments, :balance)
>
> Essentially, a shorthand for:
>
> DB[:billing_headers].filter(:billing => 5).
>    select(:charges, :payments, :balance).
>    map{|bh| [bh[:charges], bh[:payments], bh[:balance]}

For simple cases, it's easy, but it's difficult in more complex
cases.  It works in pretty much all cases now because there is only
one column returned.  Think about:

 DB[:billing_headers].get(:charges.sql_function, :payments - :balance)

I suppose you could automatically alias if you have more than 1
column, but that might have negative effects if the column is
referenced anywhere else (e.g. in a order by).

 DB[:a].join(:b, :id=>:b_id).order(:id).get(:a__id, :b__id___bid)

Here, the order(:id) is not ambiguous because the selection is "a.id,
b.id AS bid".  However, if you start aliasing a.id, since id is no
longer in the selection, it will be ambiguous, since it appears in
both of the underlying tables.

These issues are possible to work through, given enough logic in the
method, but in cases like this I think it's better to force the user
to deal with it manually using select and map.

Jeremy

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