čt 16. 10. 2025 v 6:08 odesílatel Michael Paquier <michael@paquier.xyz> napsal:
On Tue, Oct 14, 2025 at 01:13:38PM +0200, Matěj Klonfar wrote: > I can imagine this limitation is likely a holdover from the system's > evolution from physical replication where comments make no sense. However, > in logical replication walsender mode both SQL and replication statements > can be issued [1], so the current state brings the necessity to distinguish > when to inject the comment and when not to. What do you feel, are there any > unexpected impacts of extending the replication grammar with comments? > > I attached a simple patch extending the `replication/repl_scanner.l` with > following test: > > What do you feel, is that a good idea and/or are there any downsides I am > missing? Thank you all for the feedback.
A downside here is the extra maintenance that this creates. I cannot get much excited about the support of comments in the context of replication commands, TBH.
Makes sense, on the other hand, the most of the work was done in e4a8fb8fefb9 where `yyextra` was introduced to handle the context information (necessary for nested `/* */` comments). This proposal is then, in my opinion, just a small enhancement built on top of that with no significant impact to the maintenance costs.
That's just one opinion, of course, others may have a different view. Note that even if one uses "replication=database", the code falls back to the main query parser, where comments work.
I do not agree. Tried now on the current master HEAD (commit 41c674d2):
```
psql"dbname=postgres replication=database"
Border style is 2.
Line style is unicode.
psql (14.19 (Homebrew), server 19devel)
WARNING: psql major version 14, server major version 19.
Some psql features might not work.
Type "help" for help.
postgres=# /* foo */ IDENTIFY_SYSTEM;
2025-10-16 09:49:59.152 CEST [49754] ERROR:syntax error at or near "IDENTIFY_SYSTEM" at character 11
2025-10-16 09:49:59.152 CEST [49754] STATEMENT:/* foo */ IDENTIFY_SYSTEM;
The argument for rejection back then is that these commands are not for manual consumption, so we should keep the replication grammar file simpler. Perhaps there could be an argument with allowing commands when it comes to the logging of replication commands in the server logs, where comments can be used as a reference. That's a very narrow case, so I'd still argue that this is not enough to balance in favor of this proposal. Just my 2c. -- Michael
