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Re: log_min_messages per backend type

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Euler Taveira <euler@eulerto.com>
Cc: japin <japinli@hotmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org, Chao Li <li.evan.chao@gmail.com>
Date: 2026-01-17T22:02:47Z
Lists: pgsql-hackers 
On 2026-Jan-15, Euler Taveira wrote:

> +	/*
> +	 * Use a stable representation of log_min_messages. The generic level is
> +	 * always the first element and the other elements (type:level) are sorted
> +	 * by process type.
> +	 */
> +	list_sort(elemlist, string_cmp);
> +	foreach(l, elemlist)
> +	{
> +		char	   *tok = (char *) lfirst(l);
> +
> +		if (strchr(tok, ':') == NULL)
> +		{
> +			elemlist = list_delete(elemlist, tok);
> +			elemlist = lcons(tok, elemlist);
> +			break;
> +		}
> +	}

> +static int
> +string_cmp(const ListCell *a, const ListCell *b)
> +{
> +	const char *s = lfirst(a);
> +	const char *t = lfirst(b);
> +
> +	return strcmp(s, t);
> +}

I'm not opposed to this idea, but I think it should be implemented not
by sorting and then moving the first element to the top of the list, but
instead by modifying the cmp function so that the desired order is
achieved directly.  So the cmp() should return -1 if element a has no
colon, or 1 if element b has no colon, otherwise return per strcmp.
That way you can remove the foreach() block above, which is icky.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"Computing is too important to be left to men." (Karen Spärck Jones)

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Cleanup for log_min_messages changes in 38e0190ced71

  2. Allow log_min_messages to be set per process type

  3. Assign "backend" type earlier during process start-up

  4. Use integer backend type when exec'ing a postmaster child

  5. Sort guc_parameters.dat alphabetically by name

  6. Create a separate file listing backend types

  7. Replace postmaster.c's own backend type codes with BackendType