From 0dd094c4a0a4766cfb3c4932fa32af906229e3e3 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 4 Mar 2024 12:56:02 +0200
Subject: [PATCH] Remove unused ParallelWorkerInfo.pid field

The pid was originally used in error context of messages propagated
from parallel workers, but commit 292794f82b removed that. If the need
arises in the future, you can also get the pid with
"shm_mq_get_sender(pcxt->worker[i].error_mqh)->pid".
---
 src/backend/access/transam/parallel.c | 23 -----------------------
 src/include/access/parallel.h         |  1 -
 2 files changed, 24 deletions(-)

diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index cbfe6087da4..798cd86c881 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -1131,16 +1131,6 @@ HandleParallelMessage(ParallelContext *pcxt, int i, StringInfo msg)
 
 	switch (msgtype)
 	{
-		case PqMsg_BackendKeyData:
-			{
-				int32		pid = pq_getmsgint(msg, 4);
-
-				(void) pq_getmsgint(msg, 4);	/* discard cancel key */
-				(void) pq_getmsgend(msg);
-				pcxt->worker[i].pid = pid;
-				break;
-			}
-
 		case PqMsg_ErrorResponse:
 		case PqMsg_NoticeResponse:
 			{
@@ -1304,7 +1294,6 @@ ParallelWorkerMain(Datum main_arg)
 	char	   *relmapperspace;
 	char	   *uncommittedenumsspace;
 	char	   *clientconninfospace;
-	StringInfoData msgbuf;
 	char	   *session_dsm_handle_space;
 	Snapshot	tsnapshot;
 	Snapshot	asnapshot;
@@ -1369,18 +1358,6 @@ ParallelWorkerMain(Datum main_arg)
 	pq_set_parallel_leader(fps->parallel_leader_pid,
 						   fps->parallel_leader_proc_number);
 
-	/*
-	 * Send a BackendKeyData message to the process that initiated parallelism
-	 * so that it has access to our PID before it receives any other messages
-	 * from us.  Our cancel key is sent, too, since that's the way the
-	 * protocol message is defined, but it won't actually be used for anything
-	 * in this case.
-	 */
-	pq_beginmessage(&msgbuf, PqMsg_BackendKeyData);
-	pq_sendint32(&msgbuf, (int32) MyProcPid);
-	pq_sendint32(&msgbuf, (int32) MyCancelKey);
-	pq_endmessage(&msgbuf);
-
 	/*
 	 * Hooray! Primary initialization is complete.  Now, we need to set up our
 	 * backend-local state to match the original backend.
diff --git a/src/include/access/parallel.h b/src/include/access/parallel.h
index 64c6fb939ea..69ffe5498f9 100644
--- a/src/include/access/parallel.h
+++ b/src/include/access/parallel.h
@@ -26,7 +26,6 @@ typedef struct ParallelWorkerInfo
 {
 	BackgroundWorkerHandle *bgwhandle;
 	shm_mq_handle *error_mqh;
-	int32		pid;
 } ParallelWorkerInfo;
 
 typedef struct ParallelContext
-- 
2.39.5