I have identified the cause of the issue, basically, the reason is if we are doing a multi insert operation we don't set the toast cleanup until we get the last tuple of the xl_multi_insert [1]. Now, with streaming, we can process the transaction in between the multi-insert but while doing that the "change->data.tp.clear_toast_afterwards" is set to false in all the tuples in this stream. And due to this we will not clean up the toast.
Thanks. That matches my understanding too.
One simple fix could be that we can just clean the toast memory if we are processing in the streaming mode (as shown in the attached patch).
I am not entirely sure if it works correctly. I'd tried something similar, but the downstream node using
my output plugin gets NULL values for the toast columns. It's a bit hard to demonstrate that with the
test_decoding plugin, but if you have some other mechanism to test that change with an actual downstream
node receiving and applying changes, it will be useful to test with that.
