RE: Perform streaming logical transactions by background workers and parallel apply - Mailing list pgsql-hackers

On Mon, Sept 19, 2022 11:26 AM Wang, Wei/王 威 <wangw.fnst@fujitsu.com> wrote:
> 
> 
> Improved as suggested.
> 

Thanks for updating the patch. Here are some comments on 0001 patch.

1.
+        case TRANS_LEADER_SERIALIZE:
 
-        oldctx = MemoryContextSwitchTo(ApplyContext);
+            /*
+             * Notify handle methods we're processing a remote in-progress
+             * transaction.
+             */
+            in_streamed_transaction = true;
 
-        MyLogicalRepWorker->stream_fileset = palloc(sizeof(FileSet));
-        FileSetInit(MyLogicalRepWorker->stream_fileset);
+            /*
+             * Since no parallel apply worker is used for the first stream
+             * start, serialize all the changes of the transaction.
+             *
+             * Start a transaction on stream start, this transaction will be


It seems that the following comment can be removed after using switch case.
+             * Since no parallel apply worker is used for the first stream
+             * start, serialize all the changes of the transaction.

2.
+    switch (apply_action)
+    {
+        case TRANS_LEADER_SERIALIZE:
+            if (!in_streamed_transaction)
+                ereport(ERROR,
+                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
+                         errmsg_internal("STREAM STOP message without STREAM START")));

In apply_handle_stream_stop(), I think we can move this check to the beginning of
this function, to be consistent to other functions.

3. I think the some of the changes in 0005 patch can be merged to 0001 patch,
0005 patch can only contain the changes about new column 'apply_leader_pid'.

4.
+ * ParallelApplyWorkersList. After successfully, launching a new worker it's
+ * information is added to the ParallelApplyWorkersList. Once the worker

Should `it's` be `its` ?

Regards
Shi yu