## 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?
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