Fix memory leaks in scripts/vacuuming.c.

Coverity complained that the list of table names returned by
retrieve_objects() was leaked, and it's right.  Potentially this
is quite a lot of memory; however, it's not entirely clear how much
we gain by cleaning it up, since in many operating modes we're going
to need the list until the program is about to exit.  Still, it will
win in some cases, so fix the leak.

vacuuming.c is new in v19, and this patch doesn't apply at all cleanly
to the predecessor code in v18.  I'm not excited enough about the
issue to devise a back-patch.

src/bin/scripts/vacuuming.c

@@ -40,6 +40,7 @@ static SimpleStringList *retrieve_objects(PGconn *conn,
 										  vacuumingOptions *vacopts,
 										  SimpleStringList *objects,
 										  bool echo);
+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,
@@ -101,9 +102,13 @@ vacuuming_main(ConnParams *cparams, const char *dbname,
 										  concurrentCons,
 										  progname, echo, quiet);
 				if (ret != 0)
+				{
+					free_retrieved_objects(found_objs);
 					return ret;
 				}
+			}
 
+			free_retrieved_objects(found_objs);
 			return EXIT_SUCCESS;
 		}
 		else
@@ -171,6 +176,7 @@ vacuum_one_database(ConnParams *cparams,
 	int			ntups = 0;
 	const char *initcmd;
 	SimpleStringList *retobjs = NULL;
+	bool		free_retobjs = false;
 	int			ret = EXIT_SUCCESS;
 	const char *stage_commands[] = {
 		"SET default_statistics_target=1; SET vacuum_cost_delay=0;",
@@ -289,7 +295,8 @@ vacuum_one_database(ConnParams *cparams,
 	/*
 	 * If the caller provided the results of a previous catalog query, just
 	 * use that.  Otherwise, run the catalog query ourselves and set the
-	 * return variable if provided.
+	 * return variable if provided.  (If it is, then freeing the string list
+	 * becomes the caller's responsibility.)
 	 */
 	if (found_objs && *found_objs)
 		retobjs = *found_objs;
@@ -298,18 +305,22 @@ vacuum_one_database(ConnParams *cparams,
 		retobjs = retrieve_objects(conn, vacopts, objects, echo);
 		if (found_objs)
 			*found_objs = retobjs;
+		else
+			free_retobjs = true;
 	}
 
 	/*
 	 * Count the number of objects in the catalog query result.  If there are
 	 * none, we are done.
 	 */
-	for (cell = retobjs ? retobjs->head : NULL; cell; cell = cell->next)
+	for (cell = retobjs->head; cell; cell = cell->next)
 		ntups++;
 
 	if (ntups == 0)
 	{
 		PQfinish(conn);
+		if (free_retobjs)
+			free_retrieved_objects(retobjs);
 		return EXIT_SUCCESS;
 	}
 
@@ -407,6 +418,8 @@ finish:
 	ParallelSlotsTerminate(sa);
 	pg_free(sa);
 	termPQExpBuffer(&sql);
+	if (free_retobjs)
+		free_retrieved_objects(retobjs);
 
 	return ret;
 }
@@ -425,13 +438,16 @@ vacuum_all_databases(ConnParams *cparams,
 					 int concurrentCons,
 					 const char *progname, bool echo, bool quiet)
 {
+	int			ret = EXIT_SUCCESS;
 	PGconn	   *conn;
 	PGresult   *result;
+	int			numdbs;
 
 	conn = connectMaintenanceDatabase(cparams, progname, echo);
 	result = executeQuery(conn,
 						  "SELECT datname FROM pg_database WHERE datallowconn AND datconnlimit <> -2 ORDER BY 1;",
 						  echo);
+	numdbs = PQntuples(result);
 	PQfinish(conn);
 
 	if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
@@ -439,7 +455,7 @@ vacuum_all_databases(ConnParams *cparams,
 		SimpleStringList **found_objs = NULL;
 
 		if (vacopts->missing_stats_only)
-			found_objs = palloc0(PQntuples(result) * sizeof(SimpleStringList *));
+			found_objs = palloc0(numdbs * sizeof(SimpleStringList *));
 
 		/*
 		 * When analyzing all databases in stages, we analyze them all in the
@@ -451,10 +467,8 @@ vacuum_all_databases(ConnParams *cparams,
 		 */
 		for (int stage = 0; stage < ANALYZE_NUM_STAGES; stage++)
 		{
-			for (int i = 0; i < PQntuples(result); i++)
+			for (int i = 0; i < numdbs; i++)
 			{
-				int			ret;
-
 				cparams->override_dbname = PQgetvalue(result, i, 0);
 				ret = vacuum_one_database(cparams, vacopts, stage,
 										  objects,
@@ -462,16 +476,23 @@ vacuum_all_databases(ConnParams *cparams,
 										  concurrentCons,
 										  progname, echo, quiet);
 				if (ret != EXIT_SUCCESS)
-					return ret;
+					break;
 			}
+			if (ret != EXIT_SUCCESS)
+				break;
+		}
+
+		if (vacopts->missing_stats_only)
+		{
+			for (int i = 0; i < numdbs; i++)
+				free_retrieved_objects(found_objs[i]);
+			pg_free(found_objs);
 		}
 	}
 	else
 	{
-		for (int i = 0; i < PQntuples(result); i++)
+		for (int i = 0; i < numdbs; i++)
 		{
-			int			ret;
-
 			cparams->override_dbname = PQgetvalue(result, i, 0);
 			ret = vacuum_one_database(cparams, vacopts,
 									  ANALYZE_NO_STAGE,
@@ -480,13 +501,13 @@ vacuum_all_databases(ConnParams *cparams,
 									  concurrentCons,
 									  progname, echo, quiet);
 			if (ret != EXIT_SUCCESS)
-				return ret;
+				break;
 		}
 	}
 
 	PQclear(result);
 
-	return EXIT_SUCCESS;
+	return ret;
 }
 
 /*
@@ -784,6 +805,22 @@ retrieve_objects(PGconn *conn, vacuumingOptions *vacopts,
 	return found_objs;
 }
 
+/*
+ * Free the results of retrieve_objects().
+ *
+ * For caller convenience, we allow the argument to be NULL,
+ * although retrieve_objects() will never return that.
+ */
+static void
+free_retrieved_objects(SimpleStringList *list)
+{
+	if (list)
+	{
+		simple_string_list_destroy(list);
+		pg_free(list);
+	}
+}
+
 /*
  * Construct a vacuum/analyze command to run based on the given
  * options, in the given string buffer, which may contain previous garbage.