Re: Perform streaming logical transactions by background workers and parallel apply
Amit Kapila <amit.kapila16@gmail.com>
Attachments
- v48-changes_amit_1.patch (application/octet-stream) patch v48
On Fri, Nov 18, 2022 at 7:56 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Nov 16, 2022 at 1:50 PM houzj.fnst@fujitsu.com
> <houzj.fnst@fujitsu.com> wrote:
> >
> > On Tuesday, November 15, 2022 7:58 PM houzj.fnst@fujitsu.com <houzj.fnst@fujitsu.com> wrote:
> >
> > I noticed that I didn't add CHECK_FOR_INTERRUPTS while retrying send message.
> > So, attach the new version which adds that. Also attach the 0004 patch that
> > restarts logical replication with temporarily disabling the parallel apply if
> > failed to apply a transaction in parallel apply worker.
> >
>
> Few comments on v48-0001
> ======================
>
I have made quite a few changes in the comments, added some new
comments, and made other cosmetic changes in the attached patch. The
is atop v48-0001*. If these look okay to you, please include them in
the next version. Apart from these, I have a few more comments on
v48-0001*
1.
+static bool
+pa_can_start(TransactionId xid)
+{
+ if (!TransactionIdIsValid(xid))
+ return false;
The caller (see caller of pa_start_worker) already has a check that
xid passed here is valid, so I think this should be an Assert unless I
am missing something in which case it is better to add a comment here.
2. Will it be better to rename pa_start_worker() as
pa_allocate_worker() because it sometimes gets the worker from the
pool and also allocate the hash entry for worker info? That will even
match the corresponding pa_free_worker().
3.
+pa_start_subtrans(TransactionId current_xid, TransactionId top_xid)
{
...
+
+ oldctx = MemoryContextSwitchTo(ApplyContext);
+ subxactlist = lappend_xid(subxactlist, current_xid);
+ MemoryContextSwitchTo(oldctx);
...
Why do we need to allocate this list in a permanent context? IIUC, we
need to use this to maintain subxacts so that it can be later used to
find the given subxact at the time of rollback to savepoint in the
current in-progress transaction, so why do we need it beyond the
transaction being applied? If there is a reason for the same, it would
be better to add some comments for the same.
4.
+pa_stream_abort(LogicalRepStreamAbortData *abort_data)
{
...
+
+ for (i = list_length(subxactlist) - 1; i >= 0; i--)
+ {
+ TransactionId xid_tmp = lfirst_xid(list_nth_cell(subxactlist, i));
+
+ if (xid_tmp == subxid)
+ {
+ found = true;
+ break;
+ }
+ }
+
+ if (found)
+ {
+ RollbackToSavepoint(spname);
+ CommitTransactionCommand();
+ subxactlist = list_truncate(subxactlist, i + 1);
+ }
I was thinking whether we can have an Assert(false) for the not found
case but it seems if all the changes of a subxact have been skipped
then probably subxid corresponding to "rollback to savepoint" won't be
found in subxactlist and we don't need to do anything for it. If that
is the case, then probably adding a comment for it would be a good
idea, otherwise, we can probably have Assert(false) in the else case.
--
With Regards,
Amit Kapila.
Commits
GET /api/v1/messages/:b64id/commits
the thread's linked commits as JSON, with link sources.
API reference →
-
Fix invalid memory access during the shutdown of the parallel apply worker.
- 3d144c6c8602 16.0 landed
-
Fix assertion failure in apply worker.
- de63f8dadee4 16.0 landed
-
Use elog to report unexpected action in handle_streamed_transaction().
- 781ac42d43ab 16.0 landed
-
Use appropriate wait event when sending data in the apply worker.
- d9d7fe68d35e 16.0 landed
-
Allow the logical_replication_mode to be used on the subscriber.
- 9f2213a7c575 16.0 landed
-
Rename GUC logical_decoding_mode to logical_replication_mode.
- 1e8b61735cfb 16.0 landed
-
Display the leader apply worker's PID for parallel apply workers.
- d540a02a724b 16.0 landed
-
Improve the code to decide and process the apply action.
- c981d9145dea 16.0 landed
-
Document the newly added wait events added by commit 216a784829.
- cd06ccd78fcf 16.0 landed
-
Perform apply of large transactions by parallel workers.
- 216a784829c2 16.0 landed
-
Wake up a subscription's replication worker processes after DDL.
- c6e1f62e2cee 16.0 cited
-
Add copyright notices to meson files
- 8284cf5f746f 16.0 cited
-
Better document logical replication parameters
- a8500750ca0a 16.0 cited
-
Add a common function to generate the origin name.
- 776e1c8a5d14 16.0 cited
-
Harmonize parameter names in storage and AM code.
- bfcf1b34805f 16.0 cited
-
Avoid using list_length() to test for empty list.
- efd0c16becbf 16.0 cited
-
Improve two comments related to a boolean DefElem's value
- 8445f5a21d40 16.0 cited
-
Fix partition table's REPLICA IDENTITY checking on the subscriber.
- 26b3455afaa9 15.0 cited
-
Fix data inconsistency between publisher and subscriber.
- b7658c24c7c1 15.0 cited
-
Fix cache look-up failures while applying changes in logical replication.
- 5a97b1325453 15.0 cited