Composite Types in Conjunction with RowToStructByName

[jacobmikesell]

Is your feature request related to a problem? Please describe.
I'd like to be able to maintain only a stable struct mapping (with no special interfaces) even when using a composite type in the query.

Example (the names aren't great sorry):

type myOtherTable struct {
      SomeId int64
      SomeBool bool
}
type myTable struct {
     SomeField string
     TableValue []myOtherTable
}


func (x *myTable) ScanRow(rows pgx.Rows) error {
	val, err := pgx.RowToStructByName[myTable](rows)
	if err != nil {
		return err
	}
	*x = val
	return nil
}

create table my_table (pk bigserial primary key, some_field text);
create table my_other_table (pk bigserial primary key, my_fk bigint, some_bool bool);

select some_field, array_agg(mo) as table_value from
my_table inner m join my_other_table mo on m.pk = mo.my_fk

I'd like to be able to

var result myTable
pool.QueryRow("query").Scan(&myTable)

Describe the solution you'd like
I think this should be reasonable. The composite pgtype appears to have access to the column names, given that a "default" behavior (or new interface to meet) seems like it could use reflection to match to struct fields (by tag/default) instead of requiring field index matching.

Describe alternatives you've considered
I've implemented by meeting the existing interface, but it ends up creating friction when the rest of the struct maps by struct tag.

Additional context
I'm willing to put up a PR for this if the design/idea is valid and fits the ecosystem here!

[jackc]

This is already work given my_other_table and _my_other_table are registered. See pgx.Conn.LoadType and pgtype.Map.RegisterType.

• Your myOtherTable struct would need to exactly match the columns in the table.