sql: rollback past DDL causes deadlock

[knz]

The check for DDL that I introduced in #43051 was broken in #45566. Try this:

1. issue BEGIN; SELECT 1, wait for results to ensure the auto-retry is disabled

2. issue: SAVEPOINT foo; CREATE TABLE t(x INT); SELECT crdb_internal.force_retry('1h');

so far all good

3. issue: ROLLBACK TO SAVEPOINT foo

4. issue: SELECT * FROM t

boom - deadlock.

Expected either of the following:

1. "cannot rollback to savepoint after a transaction restart" (your other check)
2. "rollback after DDL is not yet supported" (my original check)
3. "t does not exist" (schema change properly rolled back)

[knz]

This is different from #24885 I think? Because we're looking at a savepoint past the begin of the txn.

[knz]

Also the severity is higher than the original report because once we announce savepoint support this pattern of txn is more likely to be issued by clients.

[andreimatei]

I think it is #24885. You don't need the force_retry() to repro, do you?
I'll try to do something about it

[andreimatei]

Closing in favor of #24885.