Re: row filtering for logical replication

On Mon, Feb 22, 2021, at 7:45 AM, Önder Kalacı wrote:
> Thanks for working on this. I did some review and testing, please see my comments below.
I appreciate your review. I'm working on a new patch set and expect to post it soon.

> I think if you are planning to keep the debug patch, there seems to be an area of improvement in the following code:
I was not planning to include the debug part, however, it would probably help to
debug some use cases. In the "row [not] matched" message, it should be DEBUG3
for a final version because it is too noisy. Since you mentioned I will inspect
and include in the main patch those DEBUG messages that could possibly be
useful for debug purposes.

>
> 4) In terms of performance, I also separately verified that the overhead seems pretty low with the final patch. I used the tests in commands_to_perf_test.sql file which I shared earlier. The steps in the file do not intend to measure the time precisely per tuple, but just to see if there is any noticeable regression while moving lots of data. The difference between (a) no filter (b) simple filter is between %1-%4, which could even be considered in the noise level.
I'm concerned about it too, I'm currently experimenting alternatives to reduce this overhead.

> 5) I guess we can by-pass the function limitation via operators. Do you see anything problematic with that? I think that should be allowed as it helps power users to create more complex replications if they need.
Yes, you can. I have to check if this user-defined operator could possibly
break the replication. I will make sure to include a test covering this case
too.

--
Euler Taveira
EDB https://www.enterprisedb.com/