Make it possible to pass *interface{} to Rows.Scan() or what is a workaround?

[georgysavva]

Hi. I am writing some kind of a wrapper on top of Rows.Scan().
In some cases I need to scan into destination with type *interface{}. For example to fill map[string]interface{} or to skip current column value and don't scan it at all.
The call can look like that:

     var s string
     var i interface{}
     err := rows.Scan(&s, &i)

Of course I am simplifying it, and in the real case I would use the reflection.
Nonetheless, currently pgx.Rows can't scan into destination with type *interface{}. I checked how sql.Rows behaves in this situation (with pgx as a driver), and it scan into *interface{} perfectly. I think it's worth implementing it in pgx.Rows too, for consistency.

If I am wrong and this was your intentional restriction, how can I implement what I need?
I can get all row values via Rows.Values() and for *inteface{} destinations assign corresponding row value from the list, but I still need to call pgx.Scan() for non *interface{} destinations and I need some kind of placeholder in place of *interface{} destinations.
Looking at the example above after I assign i from Rows.Values() I need to put something instead of &i to rows.Scan() call in order it to succeed. What would be the most efficient and elegant way to do that?

[jackc]

It's not an intentional restriction, it's just something that has never come up before.

As pgx is now you could use nil for the placeholder in Scan. That no-ops the field. Then you could use Values to get those values.

Adding support to Scan directly would probably involve a new pgtype.ScanPlan for empty interfaces that would call Get on the underlying pgtype.Value.

[georgysavva]

Thanks for the hint with nil :)
BTW I will try to add support for that feature in pgx the way you recommended.