Instead of hardcoding specific types and skipping type assertions based
on that, only check if a destination is a (sql.Scanner) after a failed
AssignTo.
This is slightly slower in the non-decoder case and *very* slightly
faster in the decoder. However, this approach is cleaner and has the
potential for further optimizations.
Specifying behavior for Status Null and Undefined is incorrect because
a Value is not required to have a Status. In addition, standard
behavior is to return nil, not pgtype.Null when the Status is
pgtype.Null.
This comes at a small expense to scanning into a type that implements
TextDecoder or BinaryDecoder but I think it is a good trade.
Before:
BenchmarkConnInfoScanInt4IntoBinaryDecoder-16 88181061 12.4 ns/op 0 B/op 0 allocs/op
BenchmarkConnInfoScanInt4IntoGoInt32-16 30402768 36.8 ns/op 0 B/op 0 allocs/op
After:
BenchmarkConnInfoScanInt4IntoBinaryDecoder-16 79859755 14.6 ns/op 0 B/op 0 allocs/op
BenchmarkConnInfoScanInt4IntoGoInt32-16 38969991 30.0 ns/op 0 B/op 0 allocs/op
pgtype.Row() was optimized for a single line use
without much ceremony at a cost of OID registration,
which is cumbersome. In practice it so much incovnenience
to create new Composite just before making a query.
So now there is just a Composite type and 2 helper methods:
- SetFields sets composite fields to values passed. This assignment
fails if types passed are not assignable to Values pgtype is
made of.
- Scan acts exactly like query.Scan, but for a composite value. Passed
values are set to values from SQL composite.
Composite() function returns a private type, which should
be registered with ConnInfo.RegisterDataType for the composite
type's OID.
All subsequent interaction with Composite types is to be done
via Row(...) function. Function return value can be either
passed as a query argument to build SQL composite value out of
individual fields or passed to Scan to read SQL composite value
back.
When passed to Scan, Row() should have first argument of type
*bool to flag NULL values returned from query.
ScanRowValue is useful when reading ROW() values with
known field types as well as composite types. It accepts
pgtype.Value arguments, where ROW() fields are written to
on successfull scan.
[]string, []int16, []int32, []int64, []int, []uint16, []uint32,
[]uint64, []uint, []float32, and []float64 are now supported in the
simple protocol like they are in the normal usage of the extended
protocol.
