Feedback-ID: ia2694551:Fastmail
Date: Tue, 9 Dec 2025 17:30:29 +0100
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>
Subject: Re: log_min_messages per backend type
Message-ID: <202512090935.k3xrtr44hxkn@alvherre.pgsql>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="ogkssrz7kzkktwbw"
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <202512090853.hk6e6t56bq5z@alvherre.pgsql>
Archived-At: 
 <https://www.postgresql.org/message-id/202512090935.k3xrtr44hxkn%40alvherre.pgsql>
Precedence: bulk


--ogkssrz7kzkktwbw
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit

BTW another thing I realized while looking this over, is that we quite
uselessly transform the integer backend type to a string, pass it as a
string using the --forkchild= argument to the child process, then parse
the string back to an int to use as an array index.  It would be much
easier to just use the integer value everywhere, as the attached shows.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"I love the Postgres community. It's all about doing things _properly_. :-)"
(David Garamond)

--ogkssrz7kzkktwbw
Content-Type: text/plain; charset=utf-8
Content-Disposition: attachment;
	filename*0="0001-Use-integers-not-strings-to-identify-backend-type.patch.";
	filename*1=nocfbot

From 4c2e63bc3c78b567e83a4d6d0df60ddeb0f51a3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=81lvaro=20Herrera?= <alvherre@kurilemu.de>
Date: Tue, 9 Dec 2025 15:29:43 +0100
Subject: [PATCH] Use integers not strings to identify backend type

---
 src/backend/postmaster/launch_backend.c | 32 +++++++++----------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 976638a58ac..3606a569758 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -162,7 +162,7 @@ static bool save_backend_variables(BackendParameters *param, int child_slot,
 #endif
 								   const void *startup_data, size_t startup_data_len);
 
-static pid_t internal_forkexec(const char *child_kind, int child_slot,
+static pid_t internal_forkexec(int child_kind, int child_slot,
 							   const void *startup_data, size_t startup_data_len,
 							   ClientSocket *client_sock);
 
@@ -217,7 +217,7 @@ postmaster_child_launch(BackendType child_type, int child_slot,
 		((BackendStartupData *) startup_data)->fork_started = GetCurrentTimestamp();
 
 #ifdef EXEC_BACKEND
-	pid = internal_forkexec(child_process_kinds[child_type].name, child_slot,
+	pid = internal_forkexec(child_type, child_slot,
 							startup_data, startup_data_len, client_sock);
 	/* the child process will arrive in SubPostmasterMain */
 #else							/* !EXEC_BACKEND */
@@ -282,7 +282,7 @@ postmaster_child_launch(BackendType child_type, int child_slot,
  * - fork():s, and then exec():s the child process
  */
 static pid_t
-internal_forkexec(const char *child_kind, int child_slot,
+internal_forkexec(int child_kind, int child_slot,
 				  const void *startup_data, size_t startup_data_len, ClientSocket *client_sock)
 {
 	static unsigned long tmpBackendFileNum = 0;
@@ -358,7 +358,7 @@ internal_forkexec(const char *child_kind, int child_slot,
 
 	/* set up argv properly */
 	argv[0] = "postgres";
-	snprintf(forkav, MAXPGPATH, "--forkchild=%s", child_kind);
+	snprintf(forkav, MAXPGPATH, "--forkchild=%d", child_kind);
 	argv[1] = forkav;
 	/* Insert temp file name after --forkchild argument */
 	argv[2] = tmpfilename;
@@ -392,7 +392,7 @@ internal_forkexec(const char *child_kind, int child_slot,
  *	 file is complete.
  */
 static pid_t
-internal_forkexec(const char *child_kind, int child_slot,
+internal_forkexec(int child_kind, int child_slot,
 				  const void *startup_data, size_t startup_data_len, ClientSocket *client_sock)
 {
 	int			retry_count = 0;
@@ -444,7 +444,7 @@ retry:
 #else
 	sprintf(paramHandleStr, "%lu", (DWORD) paramHandle);
 #endif
-	l = snprintf(cmdLine, sizeof(cmdLine) - 1, "\"%s\" --forkchild=\"%s\" %s",
+	l = snprintf(cmdLine, sizeof(cmdLine) - 1, "\"%s\" --forkchild=%d %s",
 				 postgres_exec_path, child_kind, paramHandleStr);
 	if (l >= sizeof(cmdLine))
 	{
@@ -567,8 +567,8 @@ retry:
  *			to what it would be if we'd simply forked on Unix, and then
  *			dispatch to the appropriate place.
  *
- * The first two command line arguments are expected to be "--forkchild=<name>",
- * where <name> indicates which postmaster child we are to become, and
+ * The first two command line arguments are expected to be "--forkchild=<kind>",
+ * where <kind> indicates which process type we are to become, and
  * the name of a variables file that we can read to load data that would
  * have been inherited by fork() on Unix.
  */
@@ -579,7 +579,6 @@ SubPostmasterMain(int argc, char *argv[])
 	size_t		startup_data_len;
 	char	   *child_kind;
 	BackendType child_type;
-	bool		found = false;
 	TimestampTz fork_end;
 
 	/* In EXEC_BACKEND case we will not have inherited these settings */
@@ -599,21 +598,12 @@ SubPostmasterMain(int argc, char *argv[])
 	if (argc != 3)
 		elog(FATAL, "invalid subpostmaster invocation");
 
-	/* Find the entry in child_process_kinds */
+	/* Parse the --forkchild argument to find our process type */
 	if (strncmp(argv[1], "--forkchild=", 12) != 0)
 		elog(FATAL, "invalid subpostmaster invocation (--forkchild argument missing)");
 	child_kind = argv[1] + 12;
-	found = false;
-	for (int idx = 0; idx < lengthof(child_process_kinds); idx++)
-	{
-		if (strcmp(child_process_kinds[idx].name, child_kind) == 0)
-		{
-			child_type = (BackendType) idx;
-			found = true;
-			break;
-		}
-	}
-	if (!found)
+	child_type = (BackendType) atoi(child_kind);
+	if (child_type <= B_INVALID || child_type > BACKEND_NUM_TYPES)
 		elog(ERROR, "unknown child kind %s", child_kind);
 
 	/* Read in the variables file */
-- 
2.47.3


--ogkssrz7kzkktwbw--