Re: cached plan must not change result type
| От | James Pang |
|---|---|
| Тема | Re: cached plan must not change result type |
| Дата | |
| Msg-id | CAHgTRfeJop+-t8b1v3U85_hhAL2o15R1cHqkVyhxWLj7B4KWLg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: cached plan must not change result type (Dave Cramer <davecramer@postgres.rocks>) |
| Ответы |
Re: cached plan must not change result type
|
| Список | pgsql-jdbc |
we did DDL "alter table ... alter column increase varchar(512) to varchar(1024)", after that done, hours later, new query select on this table still failed this error. From this https://jdbc.postgresql.org/documentation/server-prepare/#re-execution-of-failed-statements , looks like pgjdbc try to handle this exception and retry, but in our case, it did not happen. Could you direct me how to make this retry work? we only want new transactions,queries work that after the DDL changes.
protected boolean willHealViaReparse(SQLException e) {
if (e == null || e.getSQLState() == null) {
return false;
}
// "prepared statement \"S_2\" does not exist"
if (PSQLState.INVALID_SQL_STATEMENT_NAME.getState().equals(e.getSQLState())) {
return true;
}
if (!PSQLState.NOT_IMPLEMENTED.getState().equals(e.getSQLState())) {
return false;
}
if (!(e instanceof PSQLException)) {
return false;
}
PSQLException pe = (PSQLException) e;
ServerErrorMessage serverErrorMessage = pe.getServerErrorMessage();
if (serverErrorMessage == null) {
return false;
}
// "cached plan must not change result type"
String routine = serverErrorMessage.getRoutine();
return "RevalidateCachedQuery".equals(routine) // 9.2+
|| "RevalidateCachedPlan".equals(routine); // <= 9.1
}
if (e == null || e.getSQLState() == null) {
return false;
}
// "prepared statement \"S_2\" does not exist"
if (PSQLState.INVALID_SQL_STATEMENT_NAME.getState().equals(e.getSQLState())) {
return true;
}
if (!PSQLState.NOT_IMPLEMENTED.getState().equals(e.getSQLState())) {
return false;
}
if (!(e instanceof PSQLException)) {
return false;
}
PSQLException pe = (PSQLException) e;
ServerErrorMessage serverErrorMessage = pe.getServerErrorMessage();
if (serverErrorMessage == null) {
return false;
}
// "cached plan must not change result type"
String routine = serverErrorMessage.getRoutine();
return "RevalidateCachedQuery".equals(routine) // 9.2+
|| "RevalidateCachedPlan".equals(routine); // <= 9.1
}
Thanks,
James
Dave Cramer <davecramer@postgres.rocks> 於 2024年3月30日週六 上午12:48寫道：
On Fri, 29 Mar 2024 at 12:21, Tom Lane <tgl@sss.pgh.pa.us> wrote:Dave Cramer <davecramer@postgres.rocks> writes:
> This is really an issue that needs to be solved in the backend. The error
> is coming from PostgreSQL and what should happen is that when you alter a
> table that a server prepared statement relies on the backend should send a
> message to tell us that all of the prepared statements that rely on are now
> invalid and we can reprepare them.
This is something that can't change without a wire protocol change.
There is nothing in the protocol that allows the backend to send out
a message like "oh, that Describe I sent you awhile back? It might
be a lie now" at random times.I agree, but it's a known issue. I'm just pointing that it would be nice to have.We'd have to figure out the details.Also, what do you want to do about
race conditions --- that is, what if you fire off an Execute only
to find that one of those messages was already in flight to you?
A non-racy way to handle it might be for Bind/Execute to refuse to
run the query if its output has changed since the last Describe,
which we could check after acquiring table locks during Bind.
But we'd want to define "refuse" in a way that doesn't abort the
transaction, and that's a concept that doesn't exist in the
protocol at all.This actually sounds like the best option as we wouldn't have to fire off a message, just refuse to run the Execute in a way that doesn't abort the transaction.Dave
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