From 9201f1f5a0a0f6d0edaec1d84570e2d4cb6d6981 Mon Sep 17 00:00:00 2001
From: Dianjin Wang <wangdianjin@gmail.com>
Date: Sat, 12 Sep 2026 00:46:50 +0800
Subject: [PATCH] pg_basebackup: actually send the EXCLUDE options to the
 server

build_exclude_list() assembled the EXCLUDE clauses into a buffer of its
own, and BaseBackup() then freed that buffer without ever putting it in
the BASE_BACKUP command -- so -E/--exclude and --exclude-from were
silently ignored and every excluded path was copied anyway.

Worse than the wasted copying: gpinitstandby passes -E ./promote, and
'promote' is the name of PostgreSQL's promotion signal file. Copying the
coordinator's promote directory into the standby left a 'promote' entry
there, CheckPromoteSignal()'s stat() succeeds on a directory, and the
brand new standby coordinator promoted itself the moment it reached a
consistent state -- picking a new timeline instead of streaming, so
pg_stat_replication on the coordinator stayed empty.

Append the options to the command buffer with
AppendStringCommandOption() instead. The server has always understood a
repeated EXCLUDE (parse_basebackup_options collects them into one hash
table); only the client half was missing.

Exercised by gpinitstandby.feature:33 'gpinitstandby exclude dirs'.

Split out of #1639 (originally b432ad8d71b).
---
 src/bin/pg_basebackup/pg_basebackup.c | 60 ++++++++++-----------------
 1 file changed, 23 insertions(+), 37 deletions(-)

diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 24cd2f05258..82d9f005008 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -1705,36 +1705,24 @@ get_tablespace_mapping(const char *dir)
 }
 
 static void
-add_to_exclude_list(PQExpBufferData *buf, const char *exclude)
+add_to_exclude_list(PQExpBuffer buf, bool use_new_option_syntax,
+					const char *exclude)
 {
-	char		quoted[MAXPGPATH];
-	int			error;
-	size_t		len;
-
-	error = 1;
-	len = PQescapeStringConn(conn, quoted, exclude, MAXPGPATH, &error);
-	if (len == 0 || error != 0)
-	{
-		pg_log_error("could not process exclude \"%s\": %s",
-					 exclude, PQerrorMessage(conn));
-		exit(1);
-	}
-	appendPQExpBuffer(buf, " EXCLUDE '%s'", quoted);
+	/*
+	 * EXCLUDE may be given more than once; the server collects every
+	 * occurrence into one hash table.
+	 */
+	AppendStringCommandOption(buf, use_new_option_syntax, "EXCLUDE",
+							  unconstify(char *, exclude));
 }
 
-static char *
-build_exclude_list(void)
+static void
+append_exclude_options(PQExpBuffer buf, bool use_new_option_syntax)
 {
-	PQExpBufferData	buf;
 	int				i;
 
-	if (num_exclude == 0 && num_exclude_from == 0)
-		return "";
-
-	initPQExpBuffer(&buf);
-
 	for (i = 0; i < num_exclude; i++)
-		add_to_exclude_list(&buf, excludes[i]);
+		add_to_exclude_list(buf, use_new_option_syntax, excludes[i]);
 
 	for (i = 0; i < num_exclude_from; i++)
 	{
@@ -1763,19 +1751,11 @@ build_exclude_list(void)
 				 len--)
 				str[len - 1] = '\0';
 
-			add_to_exclude_list(&buf, str);
+			add_to_exclude_list(buf, use_new_option_syntax, str);
 		}
 
 		fclose(file);
 	}
-
-	if (PQExpBufferDataBroken(buf))
-	{
-		pg_log_error("out of memory");
-		exit(1);
-	}
-
-	return buf.data;
 }
 
 /*
@@ -1850,7 +1830,6 @@ BaseBackup(char *compression_algorithm, char *compression_detail,
 	char		xlogend[64] = {0};
 	int			minServerMajor,
 				maxServerMajor;
-	char 	   *exclude_list;
 	int			serverVersion,
 				serverMajor;
 	int			writing_to_stdout;
@@ -1994,7 +1973,17 @@ BaseBackup(char *compression_algorithm, char *compression_detail,
 									  "COMPRESSION_DETAIL",
 									  compression_detail);
 	}
-	exclude_list = build_exclude_list();
+	append_exclude_options(&buf, use_new_option_syntax);
+
+	/*
+	 * The append helpers do not exit on allocation failure; they mark the
+	 * buffer broken, which empties it and turns later appends into no-ops.
+	 * Without this check an out-of-memory would send a BASE_BACKUP carrying
+	 * none of the options built above -- including the EXCLUDEs -- instead of
+	 * failing.
+	 */
+	if (PQExpBufferDataBroken(buf))
+		pg_fatal("out of memory");
 
 	if (verbose)
 		pg_log_info("initiating base backup, waiting for checkpoint to complete");
@@ -2008,9 +1997,6 @@ BaseBackup(char *compression_algorithm, char *compression_detail,
 			fprintf(stderr, "\n");
 	}
 
-	if (exclude_list[0] != '\0')
-		free(exclude_list);
-
 	if (use_new_option_syntax && buf.len > 0)
 		basebkp = psprintf("BASE_BACKUP (%s)", buf.data);
 	else