database/sql/driver: support slices?

[snadrus]

Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   1.7

2. What operating system and processor architecture are you using (go env)?
   All

3. What did you do?

   db := ...connect to mysql db
   cursor, err := db.Query("SELECT * FROM user WHERE firstName IN (?)",
   []string{"Bob", "Matt", "Sam"})

   if err != nil { ////// Errored
   fmt.Println(err)
   return
   }
   .....

4. What did you expect to see?
   Comparing to PHP, I expected the following query's result:
   SELECT * FROM user WHERE firstName IN ('Bob', 'Matt', 'Sam')

5. What did you see instead?
   sql: converting Exec argument #0's type: unsupported type []int, a slice

[ianlancetaylor]

CC @bradfitz

[kardianos]

Related to #13567

[bradfitz]

Which database(s) support this at at the wire level? Where you send SQL with a single placeholder and an array type of values comes later?

[kardianos]

Postgresql is the main one I'm aware of, as it has native array types. MS SQL server can also support custom types that can included table valued types.

[bhcleek]

@kardianos Postgres and SQL Server (assuming the array is a custom table-valued type) would each treat that slice/array as a single scalar value. In the example given, firstName would have to be the array of names, not one of the names in the array. Postgres' array type, however, would allow ANY to match, assuming that the value was provided as an array (e.g. db.Query("SELECT * FROM user WHERE firstName = ANY (?)", pg.Array([]string{"Bob", "Matt", "Sam"})).

[gopherbot]

CL https://golang.org/cl/38533 mentions this issue.

[kardianos]

@snadrus I think this is actually fixed. go1.9 now supports custom import types so it is now up to drivers to implement. Can you confirm?