Would it make sense to support converting time.Time into sql.RawBytes? RawBytes is intended for scenarios where you want to original memory location of the byte array, but time.Time#Format is going to inevitably make a copy. I think this is the same reason you can't convert string into RawBytes.

I'll also tag the database/sql folks @kardianos @bradfitz

Change https://golang.org/cl/66830 mentions this issue: database/sql: convertAssign string and time.Time into RawBytes

I ran into the same problem. I have a package which scans all different types of columns into a resuable slice of []*sql.RawBytes. This works very well and avoids lots of allocs. But once a SQL column has the time.Time type, the scan into RawBytes fails of course. A real deal breaker.

I've implemented the fixes in convertAssign for scanning time.Time into RawBytes and also another switch case for string to RawBytes.

The conversion of time.Time into RawBytes uses no allocation. This gets checked in the test TestRawBytesAllocs.

The string->Rawbytes got a nice speed up due to the avoidance of reflection. Below is the benchmark.

Current implementation via reflection:

$ go test -v -run=🤐 -bench=Conve -count=2 -benchmem -timeout=17m
goos: darwin
goarch: amd64
pkg: database/sql
BenchmarkConvertAssign/stringRawBytes-4         	20000000	        61.7 ns/op	      16 B/op	       1 allocs/op
BenchmarkConvertAssign/stringRawBytes-4         	20000000	        61.9 ns/op	      16 B/op	       1 allocs/op
PASS
ok  	database/sql	2.618s

New implementation via the additional switch case:

$ go test -v -run=🤐 -bench=Conve -count=2 -benchmem -timeout=17m
goos: darwin
goarch: amd64
pkg: database/sql
BenchmarkConvertAssign/stringRawBytes-4         	30000000	        49.2 ns/op	      16 B/op	       1 allocs/op
BenchmarkConvertAssign/stringRawBytes-4         	30000000	        48.3 ns/op	      16 B/op	       1 allocs/op
PASS
ok  	database/sql	3.447s

This is the Benchmark function (not included in the CL):

func BenchmarkConvertAssign(b *testing.B) {
	b.Run("stringRawBytes", func(b *testing.B) {
		src := "plain-str"
		dest := make(RawBytes, 0, len(src))
		for i := 0; i < b.N; i++ {
			if err := convertAssign(&dest, src); err != nil {
				b.Fatal(err)
			}
			if src != string(dest) {
				b.Fatalf("Want %q Have %q", src, dest)
			}
			dest = dest[:0]
		}
	})
}

The CL is https://go-review.googlesource.com/c/go/+/66830

cc @kardianos