Errors related to constraints

[tredoe]

Every driver implementing "database/sql/driver" returns different messages when there are errors related to the integrity of constraints so they can not be handled easily.

So I did a proposal to add a type of error in the package "database/sql/driver" so it should be implemented by every driver.

Here it is the message with the proposal:
https://groups.google.com/forum/#!topic/golang-nuts/ECKF7N3jvjw

[arnehormann]

copied from my mailing list answer:

github.com/go-sql-driver/mysql returns what MySQL sends, there's no mapping involved.

How should this be changed?
The error code alone is insufficient to infer all information (which index, which field, which table, ...).
Parsing the error string is brittle because it may change a little between versions and there's a whole bunch of them and they are not documented AFAIK.
How should the error types providing all the useful information look?

As is, we provide http://godoc.org/github.com/go-sql-driver/mysql#MySQLError
Everything else can easily be handled by a support library that does this stuff, but I personally wouldn't want the maintenance burden in the driver.