Re: Error on failed COMMIT

On Mon, 2021-01-25 at 11:29 -0500, Dave Cramer wrote:
> Rebased against head
>
> Here's my summary of the long thread above.
>
> This change is in keeping with the SQL spec.
>
> There is an argument (Tom) that says that this will annoy more people than it will please.
> I presume this is due to the fact that libpq behaviour will change.
>
> As the author of the JDBC driver, and I believe I speak for other driver (NPGSQL for one)
> authors as well that have implemented the protocol I would argue that the current behaviour
> is more annoying.
>
> We currently have to keep state and determine if COMMIT actually failed or it ROLLED BACK.
> There are a number of async drivers that would also benefit from not having to keep state
> in the session.

I think this change makes sense, but I think everybody agrees that it does as it
makes PostgreSQL more standard compliant.

About the fear that it will break user's applications:

I think that the breakage will be minimal. All that will change is that COMMIT of
an aborted transaction raises an error.

Applications that catch an error in a transaction and roll back will not
be affected. What will be affected are applications that do *not* check for
errors in statements in a transaction, but check for errors in the COMMIT.
I think that doesn't happen often.

I agree that some people will be hurt, but I don't think it will be a major problem.

The patch applies and passes regression tests.

I wonder about the introduction of the new USER_ERROR level:

#define WARNING_CLIENT_ONLY 20 /* Warnings to be sent to client as usual, but
* never to the server log. */
-#define ERROR 21 /* user error - abort transaction; return to
+#define USER_ERROR 21
+#define ERROR 22 /* user error - abort transaction; return to
* known state */
/* Save ERROR value in PGERROR so it can be restored when Win32 includes
* modify it. We have to use a constant rather than ERROR because macros
* are expanded only when referenced outside macros.
*/
#ifdef WIN32
-#define PGERROR 21
+#define PGERROR 22
#endif
-#define FATAL 22 /* fatal error - abort process */
-#define PANIC 23 /* take down the other backends with me */
+#define FATAL 23 /* fatal error - abort process */
+#define PANIC 24 /* take down the other backends with me */

I see that without that, COMMIT AND CHAIN does not behave correctly,
since the respective regression tests fail.

But I don't understand why. I think that this needs some more comments to
make this clear.

Is this new message level something we need to allow setting for
"client_min_messages" and "log_min_messages"?

Yours,
Laurenz Albe