Feature Request: More qrm error constants

[CmpHDL]

We have a qrm.ErrNoRows, perhaps we should have more of these common errors as constants, like violating constraints.
qrm.ErrDuplicate for duplicate key value violates unique constraint, as an example.

If anyone runs into or can think of any more that are common usecase, add them to this thread!
If theres an existing way to accomplish this, let me know!

[CmpHDL]

@go-jet If you can show me how to correctly implement something like this within the lib I don't mind adding more.

[go-jet]

What do you mean by duplicate key value violates unique constraint?

[CmpHDL]

What do you mean by duplicate key value violates unique constraint?

On databases you can put constraints to help maintain correct data and in some cases optimize searches.

ALTER TABLE users
ADD UNIQUE (username);

Would add a constraint so that any ticket name would have to be unique.
If you do
INSERT INTO users (username) VALUES ('go-jet');
The query will work. If you try it again
INSERT INTO users (username) VALUES ('go-jet');
You will get a constraints error as a user with username 'go-jet' already exists.

[CmpHDL]

Here is an overview of constraints from the documentation.
https://www.postgresql.org/docs/9.4/ddl-constraints.html

[go-jet]

SQL driver is responsible for those kind of errors. Query() and Exec() methods will just forward driver errors, if there any.
Now, we could intercept driver errors, and convert those to qrm Error, but this would tightly couple jet with all existing golang database drivers. Because each database driver implements its own type of errors. Every time a new driver appears we will have to update error handling, as well as if some of the existing driver changes.
Depending of the driver, maybe, you can open a issue on a driver repo to add those errors, or you can add a check in your code:

func UniqueViolation(err error) bool {
	var pgErr *pgconn.PgError   //asuming pgx driver is used
	if errors.As(err, &pgErr) {
		if pgErr.Code == "23505" {
			return true
		}
	}
        return false
}

Or for pq driver, this library might be useful: https://github.com/omeid/pgerror

[CmpHDL]

Because each database driver implements its own type of errors. Every time a new driver appears we will have to update error handling, as well as if some of the existing driver changes.
Depending of the driver, maybe, you can open a issue on a driver repo to add those errors, or you can add a check in your code:

This is great information. Love the way you think @go-jet