Proposal: Callback function variants of existing methods for native pgx interface

[jackc]

A number of operations in pgx involve calling one method to start an operation and another to finish an operation. I'm considering adding simpler callback function variants for these operations.

In pgx transactions could be made simpler:

err := conn.BeginFunc(ctx, func(tx pgx.Tx) error {
	// Do stuff in the transaction
})
if err != nil {
	return err
}

as opposed to

tx, err := conn.Begin(ctx)
if err != nil {
	return err
}
defer tx.Rollback()

// Do stuff in the transaction

err = tx.Commit(ctx)
if err != nil {
	return err
}

It's shorter, and there are less places for errors to occur (such as forgetting the defer tx.Rollback()).

Similar changes could be made to BeginTx and to acquiring connections from pgxpool.

An even greater simplification might be possible with Query.

err := conn.QueryFunc(ctx,
	"select ...",
	[]interface{}{arg1, arg2, arg3},
	[]interface{}{&scan1, &scan2, &scan3},
	func(fields []pgproto3.FieldDescriptions) error {
		// Do stuff for each row
	},
)
if err != nil {
	return err
}

instead of

rows, err := conn.Query(ctx,
	"select ...",
	arg1, arg2, arg3,
)
if err != nil {
	return err
}
defer rows.Close()

for rows.Next() {
	err = rows.Scan(&scan1, &scan2, &scan3)
	if err != nil {
		return err
	}

	// Do stuff for each row
}

if rows.Err() != nil {
	return rows.Err()
}

It is much smaller and eliminates multiple potential error conditions such as forgetting defer rows.Close(), forgetting to check the result of Scan, forgetting to check rows.Err(), and remembering to check rows.Err() but mistakenly using local var err when reporting an error.

---

These changes would be entirely backwards compatible as it would add new functions without changing or removing existing ones.

Any thoughts or concerns about these potential additions?

[paudley]

This would simplify a lot of boilerplate code in my code bases. I like this idea a lot.

…

On Sat, Sep 5, 2020, 12:07 PM Jack Christensen ***@***.***> wrote: A number of operations in pgx involve calling one method to start an operation and another to finish an operation. I'm considering adding simpler callback function variants for these operations. In pgx transactions could be made simpler: err := conn.BeginFunc(ctx, func(tx pgx.Tx) error { // Do stuff in the transaction })if err != nil { return err } as opposed to tx, err := conn.Begin(ctx)if err != nil { return err }defer tx.Rollback() // Do stuff in the transaction err = tx.Commit(ctx)if err != nil { return err } It's shorter, and there are less places for errors to occur (such as forgetting the defer tx.Rollback()). Similar changes could be made to BeginTx and to acquiring connections from pgxpool. An even greater simplification might be possible with Query. err := conn.QueryFunc(ctx, "select ...", []interface{}{arg1, arg2, arg3}, []interface{}{&scan1, &scan2, &scan3}, func(fields []pgproto3.FieldDescriptions) error { // Do stuff for each row }, )if err != nil { return err } instead of rows, err := conn.Query(ctx, "select ...", arg1, arg2, arg3, )if err != nil { return err }defer rows.Close() for rows.Next() { err = rows.Scan(&scan1, &scan2, &scan3) if err != nil { return err } // Do stuff for each row } if rows.Err() != nil { return rows.Err() } It is much smaller and eliminates multiple potential error conditions such as forgetting defer rows.Close(), forgetting to check the result of Scan, forgetting to check rows.Err(), and remembering to check rows.Err() but mistakenly using local var err when reporting an error. ------------------------------ These changes would be entirely backwards compatible as it would add new functions without changing or removing existing ones. Any thoughts or concerns about these potential additions? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#821>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAEAZQ3LYTE7LGMGZNNVTFDSEKD53ANCNFSM4Q3H5VZA> .

[jackc]

There hasn't been much feedback on this proposal, but what little there has been has been positive.

I added QueryFunc in e8f959e.