Custom ColumnTypeScanType

[AmirUsef]

Is there a way to change the default scanType for a pgType?
for example I have a custom type for sql date types and it has implemented Scan and Value methods, but when I have a dynamic query and pass map[string]any as gorm Scan input, it still uses time.Time{} for date types.
And also for database numeric type it is using float64 which in some cases the number overflows.

[guidog]

Wrt numeric types: Go doesn't have a builtin decimal type. float64 is the largest floating point type.
If you want to use numeric, try shopspring/decimal. There are examples.

The other thing seems to be related to gorm. I don't thing pgx should start to support gorm or any other orm.

[AmirUsef]

You're right I can use decimal for numeric types and implement Scan and Value methods for my custom type. But again my query is dynamic and I dont know the output result so I have to pass map[string]any for scan type. in this case this method in pgx gets called:

func (r *Rows) ColumnTypeScanType(index int) reflect.Type {
fd := r.rows.FieldDescriptions()[index]

switch fd.DataTypeOID {
case pgtype.Float8OID:
	return reflect.TypeOf(float64(0))
case pgtype.Float4OID:
	return reflect.TypeOf(float32(0))
case pgtype.Int8OID:
	return reflect.TypeOf(int64(0))
case pgtype.Int4OID:
	return reflect.TypeOf(int32(0))
case pgtype.Int2OID:
	return reflect.TypeOf(int16(0))
case pgtype.BoolOID:
	return reflect.TypeOf(false)
case pgtype.NumericOID:
	return reflect.TypeOf(float64(0))
case pgtype.DateOID, pgtype.TimestampOID, pgtype.TimestamptzOID:
	return reflect.TypeOf(time.Time{})
case pgtype.ByteaOID:
	return reflect.TypeOf([]byte(nil))
default:
	return reflect.TypeOf("")
}

}

but this is not the behaviour I want for casting database types to golang types

[jackc]

In the native pgx interface you can entirely replace the logic any given type by registering a new Codec for that PostgreSQL OID. But I don't think you can change what you want in the stdlib adapter. AFAIK, the database/sql interface doesn't allow it.