Re: Perform streaming logical transactions by background workers and parallel apply
Peter Smith <smithpb2250@gmail.com>
Here are some review comments for v81-0001.
======
Commit Message
1.
Additionally, update the leader_pid column in pg_stat_activity as well to
display the PID of the leader apply worker for parallel apply workers.
~
Probably it should not say both "Additionally" and "as well" in the
same sentence.
======
src/backend/replication/logical/launcher.c
2.
/*
+ * Return the pid of the leader apply worker if the given pid is the pid of a
+ * parallel apply worker, otherwise return InvalidPid.
+ */
+pid_t
+GetLeaderApplyWorkerPid(pid_t pid)
+{
+ int leader_pid = InvalidPid;
+ int i;
+
+ LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+ for (i = 0; i < max_logical_replication_workers; i++)
+ {
+ LogicalRepWorker *w = &LogicalRepCtx->workers[i];
+
+ if (isParallelApplyWorker(w) && w->proc && pid == w->proc->pid)
+ {
+ leader_pid = w->leader_pid;
+ break;
+ }
+ }
+
+ LWLockRelease(LogicalRepWorkerLock);
+
+ return leader_pid;
+}
2a.
IIUC the IsParallelApplyWorker macro does nothing except check that
the leader_pid is not InvalidPid anyway, so AFAIK this algorithm does
not benefit from using this macro because we will want to return
InvalidPid anyway if the given pid matches.
So the inner condition can just say:
if (w->proc && w->proc->pid == pid)
{
leader_pid = w->leader_pid;
break;
}
~
2b.
A possible alternative comment.
BEFORE
Return the pid of the leader apply worker if the given pid is the pid
of a parallel apply worker, otherwise return InvalidPid.
AFTER
If the given pid has a leader apply worker then return the leader pid,
otherwise, return InvalidPid.
======
src/backend/utils/adt/pgstatfuncs.c
3.
@@ -434,6 +435,16 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
values[28] = Int32GetDatum(leader->pid);
nulls[28] = false;
}
+ else
+ {
+ int leader_pid = GetLeaderApplyWorkerPid(beentry->st_procpid);
+
+ if (leader_pid != InvalidPid)
+ {
+ values[28] = Int32GetDatum(leader_pid);
+ nulls[28] = false;
+ }
+
3a.
There is an existing comment preceding this if/else but it refers only
to leaders of parallel groups. Should that comment be updated to
mention the leader apply worker too?
~
3b.
It may be unrelated to this patch, but it seems strange to me that the
nulls[28]/values[28] assignments are done where they are. Every other
nulls/values assignment of this function here is pretty much in the
correct numerical order except this one, so IMO this code ought to be
relocated to later in this same function.
------
Kind Regards,
Peter Smith.
Fujitsu Australia.
Commits
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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