database/sql and query slice args

[Frank Davidson]

Is there a reason that slices aren't accepted as arguments to a db.Query() in database/sql? Seems like that would make things quite a bit easier...

Just wondering...

Frank

[Tamás Gulácsi]

What should the driver do with them?

[Tamás Gulácsi]

[Frank Davidson]

Well, I would think it would make things much easier if the first query argument was set to arr[0], the second to arr[1], etc... A mismatch in type of number would error out, I would think...

[Kelly Norton]

What is preventing you from calling db.Query with a slice?

https://play.golang.org/p/ANfdVl1e7t

On Thu, Mar 26, 2015 at 7:38 AM Frank Davidson <ffdav...@gmail.com> wrote:

Well, I would think it would make things much easier if the first query argument was set to arr[0], the second to arr[1], etc... A mismatch in type of number would error out, I would think...

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[Frank Davidson]

It can only be a slice of interface{}, correct? Why can't it just be any slice? I understand that I can convert to []interface{} by why not just let us use []string or similar and let the database decide if it's the right type?

On Thursday, March 26, 2015 at 8:46:38 AM UTC-4, Kelly Norton wrote:

What is preventing you from calling db.Query with a slice?

https://play.golang.org/p/ANfdVl1e7t

On Thu, Mar 26, 2015 at 7:38 AM Frank Davidson <ffdav...@gmail.com> wrote:

Well, I would think it would make things much easier if the first query argument was set to arr[0], the second to arr[1], etc... A mismatch in type of number would error out, I would think...

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[Tamás Gulácsi]

2015. március 27., péntek 14:33:22 UTC+1 időpontban Frank Davidson a következőt írta:

It can only be a slice of interface{}, correct? Why can't it just be any slice? I understand that I can convert to []interface{} by why not just let us use []string or similar and let the database decide if it's the right type?

By using []interface{}, you let the database decide if it's the right type...

The "why can't I just convert []string to []interface{}", it is even in the FAQ, and on this list, too.

[Frank Davidson]

I understand I can do it, but just seems unnecessary every time i want to insert a row of strings into my database I have to convert them:

t := []int{1, 2, 3, 4}
s := make([]interface{}, len(t))
for i, v := range t {
    s[i] = v
}

I just seems to me it would be a lot easier just to accept any slice, or even a struct (though I think that would probably have performance issues, perhaps).

[Carlos Castillo]

It's generally not the go way to intentionally introduce unexpected performance issues into the language.

If you want you could create a function to do the []val -> []interface{} conversions if it's that much of a bother to type the for loop all the time. 

Here is a reflective version that works with any slice or array: http://play.golang.org/p/KpDqLqQW71 . Note: it will panic if the input is not a slice or an array, and it's slower than the for loop version.