From 5c47c810568020830f9a44fa701d261bb91d1c3b Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Sun, 4 Feb 2024 18:32:16 +0100
Subject: [PATCH 2/2] WIP: pg_upgrade: No more "command too long"

Use extensive buffers to assemble command lines instead of fixed size.

Similar to the changes done for pg_rewind in a33e17f210.

XXX requires exporting appendPQExpBufferVA() from libpq
XXX should pg_upgrade be using StringInfo instead?
---
 src/bin/pg_upgrade/exec.c        | 37 ++++++++++++++++----------------
 src/interfaces/libpq/exports.txt |  1 +
 2 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index fec8dc4c2f7..2ea231d6f62 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -13,6 +13,7 @@
 
 #include "common/string.h"
 #include "pg_upgrade.h"
+#include "pqexpbuffer.h"
 
 static void check_data_dir(ClusterInfo *cluster);
 static void check_bin_dir(ClusterInfo *cluster, bool check_versions);
@@ -87,13 +88,11 @@ exec_prog(const char *log_filename, const char *opt_log_file,
 		  bool report_error, bool exit_on_error, const char *fmt,...)
 {
 	int			result = 0;
-	int			written;
 	char		log_file[MAXPGPATH];
-
-#define MAXCMDLEN (2 * MAXPGPATH)
-	char		cmd[MAXCMDLEN];
+	PQExpBufferData cmd;
 	FILE	   *log;
 	va_list		ap;
+	bool		done;
 
 #ifdef WIN32
 	static DWORD mainThreadId = 0;
@@ -105,18 +104,16 @@ exec_prog(const char *log_filename, const char *opt_log_file,
 
 	snprintf(log_file, MAXPGPATH, "%s/%s", log_opts.logdir, log_filename);
 
-	written = 0;
-	va_start(ap, fmt);
-	written += vsnprintf(cmd + written, MAXCMDLEN - written, fmt, ap);
-	va_end(ap);
-	if (written >= MAXCMDLEN)
-		pg_fatal("command too long");
-	written += snprintf(cmd + written, MAXCMDLEN - written,
-						" >> \"%s\" 2>&1", log_file);
-	if (written >= MAXCMDLEN)
-		pg_fatal("command too long");
+	initPQExpBuffer(&cmd);
+	do
+	{
+		va_start(ap, fmt);
+		done = appendPQExpBufferVA(&cmd, fmt, ap);
+		va_end(ap);
+	} while (!done);
+	appendPQExpBuffer(&cmd, " >> \"%s\" 2>&1", log_file);
 
-	pg_log(PG_VERBOSE, "%s", cmd);
+	pg_log(PG_VERBOSE, "%s", cmd.data);
 
 #ifdef WIN32
 
@@ -132,7 +129,7 @@ exec_prog(const char *log_filename, const char *opt_log_file,
 	if (mainThreadId != GetCurrentThreadId())
 	{
 		fflush(NULL);
-		result = system(cmd);
+		result = system(cmd.data);
 	}
 #endif
 
@@ -165,7 +162,7 @@ exec_prog(const char *log_filename, const char *opt_log_file,
 	if (mainThreadId == GetCurrentThreadId())
 		fprintf(log, "\n\n");
 #endif
-	fprintf(log, "command: %s\n", cmd);
+	fprintf(log, "command: %s\n", cmd.data);
 #ifdef WIN32
 	/* Are we printing "command:" after its output? */
 	if (mainThreadId != GetCurrentThreadId())
@@ -184,7 +181,7 @@ exec_prog(const char *log_filename, const char *opt_log_file,
 #endif
 	{
 		fflush(NULL);
-		result = system(cmd);
+		result = system(cmd.data);
 	}
 
 	if (result != 0 && report_error)
@@ -193,7 +190,7 @@ exec_prog(const char *log_filename, const char *opt_log_file,
 		report_status(PG_REPORT, "\n*failure*");
 		fflush(stdout);
 
-		pg_log(PG_VERBOSE, "There were problems executing \"%s\"", cmd);
+		pg_log(PG_VERBOSE, "There were problems executing \"%s\"", cmd.data);
 		if (opt_log_file)
 			pg_log(exit_on_error ? PG_FATAL : PG_REPORT,
 				   "Consult the last few lines of \"%s\" or \"%s\" for\n"
@@ -221,6 +218,8 @@ exec_prog(const char *log_filename, const char *opt_log_file,
 	fclose(log);
 #endif
 
+	termPQExpBuffer(&cmd);
+
 	return result == 0;
 }
 
diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt
index 088592deb16..2fc5130e7bf 100644
--- a/src/interfaces/libpq/exports.txt
+++ b/src/interfaces/libpq/exports.txt
@@ -193,3 +193,4 @@ PQsendClosePrepared       190
 PQsendClosePortal         191
 PQchangePassword          192
 PQsendPipelineSync        193
+appendPQExpBufferVA       194
-- 
2.43.0