Date: Mon, 8 Dec 2025 12:09:12 -0600
From: Nathan Bossart <nathandbossart@gmail.com>
To: Chao Li <li.evan.chao@gmail.com>
Cc: Corey Huinker <corey.huinker@gmail.com>, pgsql-hackers@postgresql.org
Subject: Re: vacuumdb: add --dry-run
Message-ID: <aTcUSHQniPgksgC5@nathan>
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On Sat, Dec 06, 2025 at 07:48:22AM +0800, Chao Li wrote:
> I just reviewed v5, and overall looks very good patch quality. Just a few
> nit comments on 0001 and 0003.

I've attached an updated patch set.  After giving the "dry-run" messages
another look, I think we should just print a note at the very beginning of
vacuumdb execution and leave it at that.  The per-database messages weren't
translator friendly and IMHO didn't add much, and the "-- not executed"
comments were noisy and didn't reflect the commands that would've been sent
to the server.

> Now echo and print are moved into vacopts and their default values are
> false. Here, memset() have properly initialized their values. But this
> piece of code still explicitly set boolean values to vacopts fields. So,
> to make it consistent, I feel we can also add explicit assignments to
> echo and print here, or remove those “false” assignments. This is not a
> correctness issue, just to keep in a consistent style.

We are already pretty inconsistent about this.  If anything, I think we
should do the opposite, i.e., remove any unnecessary initializations to
0/false/NULL.  The memset() makes those redundant and should suffice in
most cases.

> * As run_vacuum_command() takes both echo and dry_run, and both of them
> are defined in vcaopts, why not change this function to take a const
> vcaopts * instead of two bools?
> 
> * The function comment needs to be updated. Now it won’t always send a
> command to server, with “dry_run”, it behaves differently.

Done.

> ```
> +	if (vacopts.dry_run)
> +		pg_log_info("Executing in dry-run mode.”);
> ```
> 
> Feels like “Running” is better than “Executing”.

Done.

-- 
nathan

--jUzroBV5RYIlyQib
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v6-0001-vacuumdb-Move-some-options-to-vacuumingOptions-st.patch

From f7629cec0198cdd2f4c00a41f271cf576eb66967 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Wed, 3 Dec 2025 16:12:37 -0600
Subject: [PATCH v6 1/3] vacuumdb: Move some options to vacuumingOptions
 struct.

TODO

Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CADkLM%3DckHkX7Of5SrK7g0LokPUwJ%3Dkk8JU1GXGF5pZ1eBVr0%3DQ%40mail.gmail.com
---
 src/bin/scripts/vacuumdb.c  | 12 ++------
 src/bin/scripts/vacuuming.c | 61 ++++++++++++++++++-------------------
 src/bin/scripts/vacuuming.h |  4 ++-
 3 files changed, 36 insertions(+), 41 deletions(-)

diff --git a/src/bin/scripts/vacuumdb.c b/src/bin/scripts/vacuumdb.c
index e117dac2242..6783c843637 100644
--- a/src/bin/scripts/vacuumdb.c
+++ b/src/bin/scripts/vacuumdb.c
@@ -68,8 +68,6 @@ main(int argc, char *argv[])
 	const char *dbname = NULL;
 	const char *maintenance_db = NULL;
 	ConnParams	cparams;
-	bool		echo = false;
-	bool		quiet = false;
 	vacuumingOptions vacopts;
 	SimpleStringList objects = {NULL, NULL};
 	int			concurrentCons = 1;
@@ -78,11 +76,7 @@ main(int argc, char *argv[])
 
 	/* initialize options */
 	memset(&vacopts, 0, sizeof(vacopts));
-	vacopts.objfilter = 0;		/* no filter */
 	vacopts.parallel_workers = -1;
-	vacopts.buffer_usage_limit = NULL;
-	vacopts.no_index_cleanup = false;
-	vacopts.force_index_cleanup = false;
 	vacopts.do_truncate = true;
 	vacopts.process_main = true;
 	vacopts.process_toast = true;
@@ -110,7 +104,7 @@ main(int argc, char *argv[])
 				dbname = pg_strdup(optarg);
 				break;
 			case 'e':
-				echo = true;
+				vacopts.echo = true;
 				break;
 			case 'f':
 				vacopts.full = true;
@@ -143,7 +137,7 @@ main(int argc, char *argv[])
 					exit(1);
 				break;
 			case 'q':
-				quiet = true;
+				vacopts.quiet = true;
 				break;
 			case 't':
 				vacopts.objfilter |= OBJFILTER_TABLE;
@@ -312,7 +306,7 @@ main(int argc, char *argv[])
 	ret = vacuuming_main(&cparams, dbname, maintenance_db, &vacopts,
 						 &objects, tbl_count,
 						 concurrentCons,
-						 progname, echo, quiet);
+						 progname);
 	exit(ret);
 }
 
diff --git a/src/bin/scripts/vacuuming.c b/src/bin/scripts/vacuuming.c
index f836f21fb03..74a1f20e0f3 100644
--- a/src/bin/scripts/vacuuming.c
+++ b/src/bin/scripts/vacuuming.c
@@ -30,21 +30,20 @@ static int	vacuum_one_database(ConnParams *cparams,
 								SimpleStringList *objects,
 								SimpleStringList **found_objs,
 								int concurrentCons,
-								const char *progname, bool echo, bool quiet);
+								const char *progname);
 static int	vacuum_all_databases(ConnParams *cparams,
 								 vacuumingOptions *vacopts,
 								 SimpleStringList *objects,
 								 int concurrentCons,
-								 const char *progname, bool echo, bool quiet);
+								 const char *progname);
 static SimpleStringList *retrieve_objects(PGconn *conn,
 										  vacuumingOptions *vacopts,
-										  SimpleStringList *objects,
-										  bool echo);
+										  SimpleStringList *objects);
 static void free_retrieved_objects(SimpleStringList *list);
 static void prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
 								   vacuumingOptions *vacopts, const char *table);
-static void run_vacuum_command(PGconn *conn, const char *sql, bool echo,
-							   const char *table);
+static void run_vacuum_command(PGconn *conn, vacuumingOptions *vacopts,
+							   const char *sql, const char *table);
 
 /*
  * Executes vacuum/analyze as indicated.  Returns 0 if the plan is carried
@@ -56,7 +55,7 @@ vacuuming_main(ConnParams *cparams, const char *dbname,
 			   const char *maintenance_db, vacuumingOptions *vacopts,
 			   SimpleStringList *objects,
 			   unsigned int tbl_count, int concurrentCons,
-			   const char *progname, bool echo, bool quiet)
+			   const char *progname)
 {
 	setup_cancel_handler(NULL);
 
@@ -71,7 +70,7 @@ vacuuming_main(ConnParams *cparams, const char *dbname,
 		return vacuum_all_databases(cparams, vacopts,
 									objects,
 									concurrentCons,
-									progname, echo, quiet);
+									progname);
 	}
 	else
 	{
@@ -100,7 +99,7 @@ vacuuming_main(ConnParams *cparams, const char *dbname,
 										  objects,
 										  vacopts->missing_stats_only ? &found_objs : NULL,
 										  concurrentCons,
-										  progname, echo, quiet);
+										  progname);
 				if (ret != 0)
 				{
 					free_retrieved_objects(found_objs);
@@ -116,7 +115,7 @@ vacuuming_main(ConnParams *cparams, const char *dbname,
 									   ANALYZE_NO_STAGE,
 									   objects, NULL,
 									   concurrentCons,
-									   progname, echo, quiet);
+									   progname);
 	}
 }
 
@@ -167,7 +166,7 @@ vacuum_one_database(ConnParams *cparams,
 					SimpleStringList *objects,
 					SimpleStringList **found_objs,
 					int concurrentCons,
-					const char *progname, bool echo, bool quiet)
+					const char *progname)
 {
 	PQExpBufferData sql;
 	PGconn	   *conn;
@@ -192,7 +191,7 @@ vacuum_one_database(ConnParams *cparams,
 	Assert(stage == ANALYZE_NO_STAGE ||
 		   (stage >= 0 && stage < ANALYZE_NUM_STAGES));
 
-	conn = connectDatabase(cparams, progname, echo, false, true);
+	conn = connectDatabase(cparams, progname, vacopts->echo, false, true);
 
 	if (vacopts->disable_page_skipping && PQserverVersion(conn) < 90600)
 	{
@@ -281,7 +280,7 @@ vacuum_one_database(ConnParams *cparams,
 	/* skip_database_stats is used automatically if server supports it */
 	vacopts->skip_database_stats = (PQserverVersion(conn) >= 160000);
 
-	if (!quiet)
+	if (!vacopts->quiet)
 	{
 		if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
 			printf(_("%s: processing database \"%s\": %s\n"),
@@ -302,7 +301,7 @@ vacuum_one_database(ConnParams *cparams,
 		retobjs = *found_objs;
 	else
 	{
-		retobjs = retrieve_objects(conn, vacopts, objects, echo);
+		retobjs = retrieve_objects(conn, vacopts, objects);
 		if (found_objs)
 			*found_objs = retobjs;
 		else
@@ -341,7 +340,7 @@ vacuum_one_database(ConnParams *cparams,
 	if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
 	{
 		initcmd = stage_commands[stage];
-		executeCommand(conn, initcmd, echo);
+		executeCommand(conn, initcmd, vacopts->echo);
 	}
 	else
 		initcmd = NULL;
@@ -351,7 +350,8 @@ vacuum_one_database(ConnParams *cparams,
 	 * for the first slot.  If not in parallel mode, the first slot in the
 	 * array contains the connection.
 	 */
-	sa = ParallelSlotsSetup(concurrentCons, cparams, progname, echo, initcmd);
+	sa = ParallelSlotsSetup(concurrentCons, cparams, progname,
+							vacopts->echo, initcmd);
 	ParallelSlotsAdoptConn(sa, conn);
 
 	initPQExpBuffer(&sql);
@@ -383,8 +383,7 @@ vacuum_one_database(ConnParams *cparams,
 		 * through ParallelSlotsGetIdle.
 		 */
 		ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
-		run_vacuum_command(free_slot->connection, sql.data,
-						   echo, tabname);
+		run_vacuum_command(free_slot->connection, vacopts, sql.data, tabname);
 
 		cell = cell->next;
 	} while (cell != NULL);
@@ -408,7 +407,7 @@ vacuum_one_database(ConnParams *cparams,
 		}
 
 		ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
-		run_vacuum_command(free_slot->connection, cmd, echo, NULL);
+		run_vacuum_command(free_slot->connection, vacopts, cmd, NULL);
 
 		if (!ParallelSlotsWaitCompletion(sa))
 			ret = EXIT_FAILURE; /* error already reported by handler */
@@ -436,17 +435,17 @@ vacuum_all_databases(ConnParams *cparams,
 					 vacuumingOptions *vacopts,
 					 SimpleStringList *objects,
 					 int concurrentCons,
-					 const char *progname, bool echo, bool quiet)
+					 const char *progname)
 {
 	int			ret = EXIT_SUCCESS;
 	PGconn	   *conn;
 	PGresult   *result;
 	int			numdbs;
 
-	conn = connectMaintenanceDatabase(cparams, progname, echo);
+	conn = connectMaintenanceDatabase(cparams, progname, vacopts->echo);
 	result = executeQuery(conn,
 						  "SELECT datname FROM pg_database WHERE datallowconn AND datconnlimit <> -2 ORDER BY 1;",
-						  echo);
+						  vacopts->echo);
 	numdbs = PQntuples(result);
 	PQfinish(conn);
 
@@ -474,7 +473,7 @@ vacuum_all_databases(ConnParams *cparams,
 										  objects,
 										  vacopts->missing_stats_only ? &found_objs[i] : NULL,
 										  concurrentCons,
-										  progname, echo, quiet);
+										  progname);
 				if (ret != EXIT_SUCCESS)
 					break;
 			}
@@ -499,7 +498,7 @@ vacuum_all_databases(ConnParams *cparams,
 									  objects,
 									  NULL,
 									  concurrentCons,
-									  progname, echo, quiet);
+									  progname);
 			if (ret != EXIT_SUCCESS)
 				break;
 		}
@@ -524,7 +523,7 @@ vacuum_all_databases(ConnParams *cparams,
  */
 static SimpleStringList *
 retrieve_objects(PGconn *conn, vacuumingOptions *vacopts,
-				 SimpleStringList *objects, bool echo)
+				 SimpleStringList *objects)
 {
 	PQExpBufferData buf;
 	PQExpBufferData catalog_query;
@@ -776,10 +775,10 @@ retrieve_objects(PGconn *conn, vacuumingOptions *vacopts,
 	 * query for consistency with table lookups done elsewhere by the user.
 	 */
 	appendPQExpBufferStr(&catalog_query, " ORDER BY c.relpages DESC;");
-	executeCommand(conn, "RESET search_path;", echo);
-	res = executeQuery(conn, catalog_query.data, echo);
+	executeCommand(conn, "RESET search_path;", vacopts->echo);
+	res = executeQuery(conn, catalog_query.data, vacopts->echo);
 	termPQExpBuffer(&catalog_query);
-	PQclear(executeQuery(conn, ALWAYS_SECURE_SEARCH_PATH_SQL, echo));
+	PQclear(executeQuery(conn, ALWAYS_SECURE_SEARCH_PATH_SQL, vacopts->echo));
 
 	/*
 	 * Build qualified identifiers for each table, including the column list
@@ -1001,12 +1000,12 @@ prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
  * Any errors during command execution are reported to stderr.
  */
 static void
-run_vacuum_command(PGconn *conn, const char *sql, bool echo,
-				   const char *table)
+run_vacuum_command(PGconn *conn, vacuumingOptions *vacopts,
+				   const char *sql, const char *table)
 {
 	bool		status;
 
-	if (echo)
+	if (vacopts->echo)
 		printf("%s\n", sql);
 
 	status = PQsendQuery(conn, sql) == 1;
diff --git a/src/bin/scripts/vacuuming.h b/src/bin/scripts/vacuuming.h
index 49f968b32e5..90db4fa1a64 100644
--- a/src/bin/scripts/vacuuming.h
+++ b/src/bin/scripts/vacuuming.h
@@ -51,6 +51,8 @@ typedef struct vacuumingOptions
 	bool		skip_database_stats;
 	char	   *buffer_usage_limit;
 	bool		missing_stats_only;
+	bool		echo;
+	bool		quiet;
 } vacuumingOptions;
 
 /* Valid values for vacuumingOptions->objfilter */
@@ -65,7 +67,7 @@ extern int	vacuuming_main(ConnParams *cparams, const char *dbname,
 						   SimpleStringList *objects,
 						   unsigned int tbl_count,
 						   int concurrentCons,
-						   const char *progname, bool echo, bool quiet);
+						   const char *progname);
 
 extern char *escape_quotes(const char *src);
 
-- 
2.39.5 (Apple Git-154)


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Content-Disposition: attachment;
	filename=v6-0002-Add-ParallelSlotSetIdle.patch

From 355e93d9a9ff61019520f76edd690fafd0399790 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Thu, 20 Nov 2025 14:16:02 -0600
Subject: [PATCH v6 2/3] Add ParallelSlotSetIdle().

TODO

Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com
Discussion: https://postgr.es/m/CADkLM%3DckHkX7Of5SrK7g0LokPUwJ%3Dkk8JU1GXGF5pZ1eBVr0%3DQ%40mail.gmail.com
---
 src/fe_utils/parallel_slot.c         | 6 ++----
 src/include/fe_utils/parallel_slot.h | 7 +++++++
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/fe_utils/parallel_slot.c b/src/fe_utils/parallel_slot.c
index 253a840865e..1b9bc8b0da8 100644
--- a/src/fe_utils/parallel_slot.c
+++ b/src/fe_utils/parallel_slot.c
@@ -269,8 +269,7 @@ wait_on_slots(ParallelSlotArray *sa)
 			else
 			{
 				/* This connection has become idle */
-				sa->slots[i].inUse = false;
-				ParallelSlotClearHandler(&sa->slots[i]);
+				ParallelSlotSetIdle(&sa->slots[i]);
 				break;
 			}
 		}
@@ -509,8 +508,7 @@ ParallelSlotsWaitCompletion(ParallelSlotArray *sa)
 		if (!consumeQueryResult(&sa->slots[i]))
 			return false;
 		/* Mark connection as idle */
-		sa->slots[i].inUse = false;
-		ParallelSlotClearHandler(&sa->slots[i]);
+		ParallelSlotSetIdle(&sa->slots[i]);
 	}
 
 	return true;
diff --git a/src/include/fe_utils/parallel_slot.h b/src/include/fe_utils/parallel_slot.h
index 7770a20de34..4a5fbfb3d8c 100644
--- a/src/include/fe_utils/parallel_slot.h
+++ b/src/include/fe_utils/parallel_slot.h
@@ -58,6 +58,13 @@ ParallelSlotClearHandler(ParallelSlot *slot)
 	slot->handler_context = NULL;
 }
 
+static inline void
+ParallelSlotSetIdle(ParallelSlot *slot)
+{
+	slot->inUse = false;
+	ParallelSlotClearHandler(slot);
+}
+
 extern ParallelSlot *ParallelSlotsGetIdle(ParallelSlotArray *sa,
 										  const char *dbname);
 
-- 
2.39.5 (Apple Git-154)


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Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename=v6-0003-vacuumdb-Add-dry-run.patch

From df0228f6378ffa1861dd5afc2dfd3187d6fa943b Mon Sep 17 00:00:00 2001
From: Corey Huinker <corey.huinker@gmail.com>
Date: Mon, 10 Nov 2025 14:33:41 -0500
Subject: [PATCH v6 3/3] vacuumdb: Add --dry-run.

TODO

Author: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Discussion: https://postgr.es/m/CADkLM%3DckHkX7Of5SrK7g0LokPUwJ%3Dkk8JU1GXGF5pZ1eBVr0%3DQ%40mail.gmail.com
---
 doc/src/sgml/ref/vacuumdb.sgml    | 10 ++++++++++
 src/bin/scripts/t/100_vacuumdb.pl | 12 ++++++++++++
 src/bin/scripts/vacuumdb.c        |  8 ++++++++
 src/bin/scripts/vacuuming.c       | 30 ++++++++++++++++++++----------
 src/bin/scripts/vacuuming.h       |  1 +
 5 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/doc/src/sgml/ref/vacuumdb.sgml b/doc/src/sgml/ref/vacuumdb.sgml
index 84c76d7350c..508c8dfa146 100644
--- a/doc/src/sgml/ref/vacuumdb.sgml
+++ b/doc/src/sgml/ref/vacuumdb.sgml
@@ -171,6 +171,16 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>--dry-run</option></term>
+      <listitem>
+       <para>
+        Print, but do not execute, the vacuum and analyze commands that would
+        have been sent to the server.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>-e</option></term>
       <term><option>--echo</option></term>
diff --git a/src/bin/scripts/t/100_vacuumdb.pl b/src/bin/scripts/t/100_vacuumdb.pl
index a16fad593f7..fb2fecdd3c6 100644
--- a/src/bin/scripts/t/100_vacuumdb.pl
+++ b/src/bin/scripts/t/100_vacuumdb.pl
@@ -169,6 +169,10 @@ $node->issues_sql_like(
 	[ 'vacuumdb', '--schema' => '"Foo"', 'postgres' ],
 	qr/VACUUM \(SKIP_DATABASE_STATS\) "Foo".bar/,
 	'vacuumdb --schema');
+$node->issues_sql_unlike(
+	[ 'vacuumdb', '--schema' => '"Foo"', 'postgres', '--dry-run' ],
+	qr/VACUUM \(SKIP_DATABASE_STATS\) "Foo".bar/,
+	'vacuumdb --dry-run');
 $node->issues_sql_like(
 	[ 'vacuumdb', '--schema' => '"Foo"', '--schema' => '"Bar"', 'postgres' ],
 	qr/VACUUM\ \(SKIP_DATABASE_STATS\)\ "Foo".bar
@@ -241,6 +245,14 @@ $node->safe_psql('postgres', q|
   CREATE TABLE regression_vacuumdb_test AS select generate_series(1, 10) a, generate_series(2, 11) b;
   ALTER TABLE regression_vacuumdb_test ADD COLUMN c INT GENERATED ALWAYS AS (a + b);
 |);
+$node->issues_sql_unlike(
+	[
+		'vacuumdb', '--analyze-only', '--dry-run',
+		'--missing-stats-only', '-t',
+		'regression_vacuumdb_test', 'postgres'
+	],
+	qr/statement:\ ANALYZE/sx,
+	'--missing-stats-only --dry-run');
 $node->issues_sql_like(
 	[
 		'vacuumdb', '--analyze-only',
diff --git a/src/bin/scripts/vacuumdb.c b/src/bin/scripts/vacuumdb.c
index 6783c843637..6e4c809e806 100644
--- a/src/bin/scripts/vacuumdb.c
+++ b/src/bin/scripts/vacuumdb.c
@@ -59,6 +59,7 @@ main(int argc, char *argv[])
 		{"no-process-main", no_argument, NULL, 12},
 		{"buffer-usage-limit", required_argument, NULL, 13},
 		{"missing-stats-only", no_argument, NULL, 14},
+		{"dry-run", no_argument, NULL, 15},
 		{NULL, 0, NULL, 0}
 	};
 
@@ -207,6 +208,9 @@ main(int argc, char *argv[])
 			case 14:
 				vacopts.missing_stats_only = true;
 				break;
+			case 15:
+				vacopts.dry_run = true;
+				break;
 			default:
 				/* getopt_long already emitted a complaint */
 				pg_log_error_hint("Try \"%s --help\" for more information.", progname);
@@ -303,6 +307,9 @@ main(int argc, char *argv[])
 		pg_fatal("cannot use the \"%s\" option without \"%s\" or \"%s\"",
 				 "missing-stats-only", "analyze-only", "analyze-in-stages");
 
+	if (vacopts.dry_run && !vacopts.quiet)
+		pg_log_info("Running in dry-run mode.");
+
 	ret = vacuuming_main(&cparams, dbname, maintenance_db, &vacopts,
 						 &objects, tbl_count,
 						 concurrentCons,
@@ -345,6 +352,7 @@ help(const char *progname)
 	printf(_("      --buffer-usage-limit=SIZE   size of ring buffer used for vacuum\n"));
 	printf(_("  -d, --dbname=DBNAME             database to vacuum\n"));
 	printf(_("      --disable-page-skipping     disable all page-skipping behavior\n"));
+	printf(_("      --dry-run                   show the commands that would be sent to the server\n"));
 	printf(_("  -e, --echo                      show the commands being sent to the server\n"));
 	printf(_("  -f, --full                      do full vacuuming\n"));
 	printf(_("  -F, --freeze                    freeze row transaction information\n"));
diff --git a/src/bin/scripts/vacuuming.c b/src/bin/scripts/vacuuming.c
index 74a1f20e0f3..73239e86e0a 100644
--- a/src/bin/scripts/vacuuming.c
+++ b/src/bin/scripts/vacuuming.c
@@ -42,8 +42,9 @@ static SimpleStringList *retrieve_objects(PGconn *conn,
 static void free_retrieved_objects(SimpleStringList *list);
 static void prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
 								   vacuumingOptions *vacopts, const char *table);
-static void run_vacuum_command(PGconn *conn, vacuumingOptions *vacopts,
-							   const char *sql, const char *table);
+static void run_vacuum_command(ParallelSlot *free_slot,
+							   vacuumingOptions *vacopts, const char *sql,
+							   const char *table);
 
 /*
  * Executes vacuum/analyze as indicated.  Returns 0 if the plan is carried
@@ -340,7 +341,11 @@ vacuum_one_database(ConnParams *cparams,
 	if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
 	{
 		initcmd = stage_commands[stage];
-		executeCommand(conn, initcmd, vacopts->echo);
+
+		if (vacopts->dry_run)
+			printf("%s\n", initcmd);
+		else
+			executeCommand(conn, initcmd, vacopts->echo);
 	}
 	else
 		initcmd = NULL;
@@ -383,7 +388,7 @@ vacuum_one_database(ConnParams *cparams,
 		 * through ParallelSlotsGetIdle.
 		 */
 		ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
-		run_vacuum_command(free_slot->connection, vacopts, sql.data, tabname);
+		run_vacuum_command(free_slot, vacopts, sql.data, tabname);
 
 		cell = cell->next;
 	} while (cell != NULL);
@@ -407,7 +412,7 @@ vacuum_one_database(ConnParams *cparams,
 		}
 
 		ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
-		run_vacuum_command(free_slot->connection, vacopts, cmd, NULL);
+		run_vacuum_command(free_slot, vacopts, cmd, NULL);
 
 		if (!ParallelSlotsWaitCompletion(sa))
 			ret = EXIT_FAILURE; /* error already reported by handler */
@@ -995,20 +1000,25 @@ prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
 
 /*
  * Send a vacuum/analyze command to the server, returning after sending the
- * command.
+ * command.  If dry_run is true, the command is printed but not sent to the
+ * server.
  *
  * Any errors during command execution are reported to stderr.
  */
 static void
-run_vacuum_command(PGconn *conn, vacuumingOptions *vacopts,
+run_vacuum_command(ParallelSlot *free_slot, vacuumingOptions *vacopts,
 				   const char *sql, const char *table)
 {
-	bool		status;
+	bool		status = true;
+	PGconn	   *conn = free_slot->connection;
 
-	if (vacopts->echo)
+	if (vacopts->echo || vacopts->dry_run)
 		printf("%s\n", sql);
 
-	status = PQsendQuery(conn, sql) == 1;
+	if (vacopts->dry_run)
+		ParallelSlotSetIdle(free_slot);
+	else
+		status = PQsendQuery(conn, sql) == 1;
 
 	if (!status)
 	{
diff --git a/src/bin/scripts/vacuuming.h b/src/bin/scripts/vacuuming.h
index 90db4fa1a64..586b6caa3d6 100644
--- a/src/bin/scripts/vacuuming.h
+++ b/src/bin/scripts/vacuuming.h
@@ -53,6 +53,7 @@ typedef struct vacuumingOptions
 	bool		missing_stats_only;
 	bool		echo;
 	bool		quiet;
+	bool		dry_run;
 } vacuumingOptions;
 
 /* Valid values for vacuumingOptions->objfilter */
-- 
2.39.5 (Apple Git-154)


--jUzroBV5RYIlyQib--