This may be helpful.
https://godoc.org/github.com/golang-sql/sqlexp#Querier
On Thu, Jan 16, 2020 at 1:09 AM Tamás Gulácsi <tgulacs...@gmail.com> wrote:
> 2020. január 16., csütörtök 8:20:17 UTC+1 időpontban Shulhan a következőt
> írta:
>>
>> ## Problem
>>
>> At some point we have a function that receive an instance of database
>> connection to query rows in specific table.
>>
>> Let's say that function F() accept DB that query table T.
>>
>> If function F() called with DB instance, it will query only rows that has
>> been committed into database.
>>
>> IF function F() called with Tx instance, it will query all rows including
>> the one that has not been committed yet into database.
>>
>> Since DB and Tx are different types, we will have two functions that
>> almost have identical code,
>>
>> func F(db *sql.DB) (output int) {
>> q := `SELECT … FROM T WHERE …`
>> err := db.QueryRow(q).Scan(&output)
>> …
>> return output
>> }
>>
>> func FWithTx(tx *sql.Tx)(output int) {
>> q := `SELECT … FROM T WHERE …`
>> err := tx.QueryRow(q).Scan(&output)
>> …
>> return output
>> }
>>
>>
>> ## Proposed solution
>>
>> Add an interface Session (the name is not fixed yet) to package sql with
>> the following signature,
>>
>> type Session interface {
>> func Exec(query string, args ...interface{}) (Result, error)
>> func ExecContext(ctx context.Context, query string, args
>> ...interface{}) (Result, error)
>> func Prepare(query string) (*Stmt, error)
>> func PrepareContext(ctx context.Context, query string) (*Stmt, error)
>> func Query(query string, args ...interface{}) (*Rows, error)
>> func QueryContext(ctx context.Context, query string, args
>> ...interface{}) (*Rows, error)
>> func QueryRow(query string, args ...interface{}) *Row
>> func QueryRowContext(ctx context.Context, query string, args
>> ...interface{}) *Row
>> }
>>
>> Session interface is combination of DB and Tx that contains all identical
>> methods.
>>
>>
>> ## Rationale
>>
>> Without Session, user will have two functions that have the same code,
>>
>> By using Session, we can minimise duplicate code in the user level. for
>> example using the previous problems definition the function F() become one,
>>
>> func F(session sql.Session)(output int) {
>> q := `SELECT … FROM T WHERE …`
>> err := session.QueryRow().Scan(&output)
>> …
>> return output
>> }
>>
>>
>> ## Discussion
>>
>> Any thought about this proposal?
>
>
>
> Just define the interface and use it - Go is not Java, iff a type
> statisfies an interface, then it also implements it!
>
> You can use anonymous interfaces also!
>
> ```
> func F(db interface { QueryRow() *sql.Row })(output int) {
> q := `SELECT … FROM T WHERE …`
> err := db.QueryRow().Scan(&
>>
>> output)
>> …
>> return output
>> }
>
> ```
>
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- a.
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