Re: log_min_messages per backend type

Hi Euler,

I just reviewed the patch and got a few comments.

> On Nov 6, 2025, at 21:09, Euler Taveira <euler(at)eulerto(dot)com> wrote:
>
> On Sun, Oct 5, 2025, at 11:18 AM, Euler Taveira wrote:
>> This new patch contains the following changes:
>>
>> - patch was rebased
>> - use commit dbf8cfb4f02
>> - use some GUC memory allocation functions
>> - avoid one memory allocation (suggested by Japin Li)
>> - rename backend type: logger -> syslogger
>> - adjust tests to increase test coverage
>> - improve documentation and comments to reflect the current state
>>
>
> Patch was rebased since commit fce7c73fba4 broke it. No modifications.
>
>
> --
> Euler Taveira
> EDB https://www.enterprisedb.com/<v5-0001-log_min_messages-per-backend-type.patch>

1 - variable.c
```
+ /* Initialize the array. */
+ memset(newlevel, WARNING, BACKEND_NUM_TYPES * sizeof(int));
```

I think this statement is wrong, because memset() writes bytes but integers, so this statement will set very byte to WARNING, which should not be the intention. You will need to use a loop to initialize every element of newlevel.

2 - variable.c
```
+ /* Parse string into list of identifiers. */
+ if (!SplitGUCList(rawstring, ',', &elemlist))
+ {
+ /* syntax error in list */
+ GUC_check_errdetail("List syntax is invalid.");
+ guc_free(rawstring);
+ list_free(elemlist);
+ return false;
+ }
```

Every element of elemlist points to a position of rawstring, so it’s better to list_free(elemlist) first then guc_free(rawstring).

3 - launch_backend.c
```
static inline bool
should_output_to_server(int elevel)
{
- return is_log_level_output(elevel, log_min_messages);
+ return is_log_level_output(elevel, log_min_messages[MyBackendType]);
}
```

Is it possible that when this function is called, MyBackendType has not been initialized? To be safe, maybe we can check if MyBackendType is 0 (B_INVALID), then use the generic log_min_message.

4 - config.sgml
```
+ Valid values are a comma-separated list of <literal>backendtype:level</literal>
+ and a single <literal>level</literal>. The list allows it to use
+ different levels per backend type. Only the single <literal>level</literal>
+ is mandatory (order does not matter) and it is assigned to the backend
+ types that are not specified in the list.
+ Valid <literal>backendtype</literal> values are <literal>archiver</literal>,
+ <literal>autovacuum</literal>, <literal>backend</literal>,
+ <literal>bgworker</literal>, <literal>bgwriter</literal>,
+ <literal>checkpointer</literal>, <literal>ioworker</literal>,
+ <literal>syslogger</literal>, <literal>slotsyncworker</literal>,
+ <literal>startup</literal>, <literal>walreceiver</literal>,
+ <literal>walsender</literal>, <literal>walsummarizer</literal>, and
+ <literal>walwriter</literal>.
+ Valid <literal>level</literal> values are <literal>DEBUG5</literal>,
+ <literal>DEBUG4</literal>, <literal>DEBUG3</literal>, <literal>DEBUG2</literal>,
+ <literal>DEBUG1</literal>, <literal>INFO</literal>, <literal>NOTICE</literal>,
+ <literal>WARNING</literal>, <literal>ERROR</literal>, <literal>LOG</literal>,
+ <literal>FATAL</literal>, and <literal>PANIC</literal>. Each level includes
+ all the levels that follow it. The later the level, the fewer messages are sent
+ to the log. The default is <literal>WARNING</literal> for all backend types.
+ Note that <literal>LOG</literal> has a different rank here than in
```

* “Valid values are …”, here “are” usually mean both are needed, so maybe change “are” to “can be”.
* It says “the single level is mandatory”, then why there is still a default value?

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/