RE: Perform streaming logical transactions by background workers and parallel apply

On Tuesday, October 18, 2022 10:36 AM Peter Smith <smithpb2250@gmail.com> wrote:
> 
> Hi, here are my review comments for patch v38-0001.

Thanks for the comments.

> ~~~
> 
> 12. get_transaction_apply_action
> 
> I still felt like there should be some tablesync checks/comments in
> this function, just for sanity, even if it works as-is now.
> 
> For example, are you saying ([3] #22b) that there might be rare cases
> where a Tablesync would call to parallel_apply_find_worker? That seems
> strange, given that "for streaming transactions that are being applied
> in the parallel ... we disallow applying changes on a table that is
> not in the READY state".
> 
> ------

I think because we won't try to start parallel apply worker in table sync
worker(see the check in parallel_apply_can_start()), so we won't find any
worker in parallel_apply_find_worker() which means get_transaction_apply_action
will return TRANS_LEADER_SERIALIZE. And get_transaction_apply_action is a
function which can be invoked for all kinds of workers(same is true for all
apply_handle_xxx functions), so not sure if table sync check/comment is
necessary.

Best regards,
Hou zj