Change bgw_log_level to use PGC_SUSET

Right now `bgw_log_level` requires `ALTER SYSTEM` since it is using
`PGC_SIGHUP` but we want to make sure that it is possible to set the
scheduler log level using `ALTER DATABASE` which allows it to be
replicated.

Since we want to allow configuration to be reloaded without restarting
the server, we are limited to `PGC_SUSET` and `PGC_SIGHUP`.

.unreleased/fix_6384

@@ -0,0 +1 @@
+Fixes: #6384 Change bgw_log_level to use PGC_SUSET

src/guc.c

@@ -742,7 +742,7 @@ _guc_init(void)
 							 /* valueAddr= */ &ts_guc_bgw_log_level,
 							 /* bootValue= */ WARNING,
 							 /* options= */ loglevel_options,
-							 /* context= */ PGC_SIGHUP,
+							 /* context= */ PGC_SUSET,
 							 0,
 							 NULL,
 							 NULL,

tsl/test/expected/bgw_scheduler_control.out

@@ -10,6 +10,7 @@ CREATE FUNCTION ts_bgw_params_destroy() RETURNS VOID
 AS :MODULE_PATHNAME LANGUAGE C VOLATILE;
 CREATE FUNCTION ts_bgw_params_reset_time(set_time BIGINT, wait BOOLEAN) RETURNS VOID
 AS :MODULE_PATHNAME LANGUAGE C VOLATILE;
+ALTER DATABASE :TEST_DBNAME OWNER TO :ROLE_DEFAULT_PERM_USER;
 -- These are needed to set up the test scheduler
 CREATE TABLE public.bgw_dsm_handle_store(handle BIGINT);
 INSERT INTO public.bgw_dsm_handle_store VALUES (0);
@@ -40,7 +41,7 @@ TRUNCATE _timescaledb_internal.bgw_job_stat;
 -- Debug messages should be in log now which it wasn't before.
 --
 \c :TEST_DBNAME :ROLE_SUPERUSER
-ALTER SYSTEM SET timescaledb.bgw_log_level = 'DEBUG1';
+ALTER DATABASE :TEST_DBNAME SET timescaledb.bgw_log_level = 'DEBUG1';
 SELECT pg_reload_conf();
  pg_reload_conf 
 ----------------
@@ -94,7 +95,7 @@ SELECT * FROM cleaned_bgw_log;
       4 | DB Scheduler     | database scheduler for database (RANDOM) exiting
 (7 rows)
 
-ALTER SYSTEM RESET timescaledb.bgw_log_level;
+ALTER DATABASE :TEST_DBNAME RESET timescaledb.bgw_log_level;
 SELECT pg_reload_conf();
  pg_reload_conf 
 ----------------
@@ -126,3 +127,8 @@ SELECT delete_job(:job_id);
 
 (1 row)
 
+-- Make sure we can set the variable using ALTER SYSTEM. We don't
+-- bother about checking that it has an effect here since we already
+-- knows it works from the above code.
+ALTER SYSTEM SET timescaledb.bgw_log_level TO 'DEBUG2';
+ALTER SYSTEM RESET timescaledb.bgw_log_level;

tsl/test/sql/bgw_scheduler_control.sql

@@ -15,6 +15,8 @@ AS :MODULE_PATHNAME LANGUAGE C VOLATILE;
 CREATE FUNCTION ts_bgw_params_reset_time(set_time BIGINT, wait BOOLEAN) RETURNS VOID
 AS :MODULE_PATHNAME LANGUAGE C VOLATILE;
 
+ALTER DATABASE :TEST_DBNAME OWNER TO :ROLE_DEFAULT_PERM_USER;
+
 -- These are needed to set up the test scheduler
 CREATE TABLE public.bgw_dsm_handle_store(handle BIGINT);
 INSERT INTO public.bgw_dsm_handle_store VALUES (0);
@@ -44,7 +46,7 @@ TRUNCATE _timescaledb_internal.bgw_job_stat;
 -- Debug messages should be in log now which it wasn't before.
 --
 \c :TEST_DBNAME :ROLE_SUPERUSER
-ALTER SYSTEM SET timescaledb.bgw_log_level = 'DEBUG1';
+ALTER DATABASE :TEST_DBNAME SET timescaledb.bgw_log_level = 'DEBUG1';
 SELECT pg_reload_conf();
 
 SELECT ts_bgw_params_reset_time(0, false);
@@ -75,7 +77,7 @@ INSERT INTO _timescaledb_config.bgw_job(
 SELECT ts_bgw_db_scheduler_test_run_and_wait_for_scheduler_finish(25, 0);
 SELECT * FROM cleaned_bgw_log;
 
-ALTER SYSTEM RESET timescaledb.bgw_log_level;
+ALTER DATABASE :TEST_DBNAME RESET timescaledb.bgw_log_level;
 SELECT pg_reload_conf();
 
 TRUNCATE bgw_log;
@@ -84,3 +86,9 @@ SELECT ts_bgw_db_scheduler_test_run_and_wait_for_scheduler_finish(25, 0);
 SELECT * FROM cleaned_bgw_log;
 
 SELECT delete_job(:job_id);
+
+-- Make sure we can set the variable using ALTER SYSTEM. We don't
+-- bother about checking that it has an effect here since we already
+-- knows it works from the above code.
+ALTER SYSTEM SET timescaledb.bgw_log_level TO 'DEBUG2';
+ALTER SYSTEM RESET timescaledb.bgw_log_level;