[Solar-talk] Restricting selected cols in Solar_Sql_Table

[Rodrigo Moraes]

An addendum:
The point of adding something like setSelectedCols (or a better name)
is to offer a simple API to restrict selected columns in
Solar_Sql_Table, specially when:

  * you already have a table instance in hands (you wouldn't need to
start Solar_Sql_Select by hand in many cases);

  * you want to save resources when your table have peripheral cols
that are not needed all the time (usually filled with meta data);

  * select foreign data without loading the whole foreign table.

Of course, the main purpose is to save resources and improve
performance while providing the nice API we are used to. ;-)

rodrigo