Improving the performance of rows.Scan() in Go

I have a very simple query that returns a couple thousand rows with only two columns:

SELECT "id", "value" FROM "table" LIMIT 10000;

After issuing sql.Query(), I traverse the result set with the following code:

data := map[uint8]string{}

for rows.Next() {
	var (
		id     uint8
		value  string
	)

	if error := rows.Scan(&id, &value); error == nil {
		data[id] = value
	}
}

If I run the exact same query directly on the database, I get all results back within a couple of milliseconds, but the Go code takes far longer complete, sometimes almost 10 seconds!

I started commenting out several parts of the code and it seems that rows.Scan() is the culprit.

> Scan copies the columns in the current row into the values pointed at
> by dest.
>
> If an argument has type *[]byte, Scan saves in that argument a copy of
> the corresponding data. The copy is owned by the caller and can be
> modified and held indefinitely. The copy can be avoided by using an
> argument of type *RawBytes instead; see the documentation for RawBytes
> for restrictions on its use. If an argument has type *interface{},
> Scan copies the value provided by the underlying driver without
> conversion. If the value is of type []byte, a copy is made and the
> caller owns the result.

Can any expect any speed improvement if I use *[]byte, *RawBytes or *interface{} instead?

Looking at the code, it looks like the convertAssign() function is doing a lot of stuff that isn't necessary for this particular query. So my question is: how can I make the Scan process faster?

I thought about overloading the function to expect predetermined types, but that isn't possible in Go...

Any ideas?

yes, you can use RawBytes instead and rows.Scan() will avoid memory allocation/copying

About convertAssign() function - yes, its not optimal in Go 1.2,
but they make significant improvements in 1.3:

• http://code.google.com/p/go/issues/detail?id=7086
• Lock-less implementation for sync.Pool

I have some example of RawBytes usage - https://gist.github.com/yvasiyarov/9911956

This code read data from MySQL table, make some processing and write it to CSV files.
Last night it takes 1 minute 24 seconds to generate 4GB of CSV data(about 30 million rows)

so I'm pretty sure what problem is outside of go code: even worse possible usage of rows.Scan() can not give you 10 seconds delay.