How to use RowToMap with a custom map definition

[jflambert]

Sample SQL: select id from table; (where id is a UUID)

Desired map type: map[pgtype.UUID]struct{}

Reason: Caching a table's PKs in memory using a struct{} map.

From what I can see, RowToMap imposes map[string]any as a return so I can't use my "custom" map definition.

Alternative is to use pgx.CollectRows(rows, pgx.RowTo[pgtype.UUID]) and loop through the []pgtype.UUID slice to set the map. But I was hoping there could be a more direct approach.

Could RowTo by itself be used?

[jackc]

RowToMap is designed to represent each row as a key-value pair. It's not what you are looking for.

What you are really looking for is a version of CollectRows that collects into a map instead of a slice. The code for CollectRows is pretty simple, you can either copy and change that or use rows.Next() and rows.Scan() directly.

[jflambert]

OK thanks for the answer! I ended up using next/scan as I actually needed a couple of different map types, and I'm not incredibly comfortable with generics yet.