Load hypercore handler eagerly

If a crossmodule wrapper function is called as part of a query on a
fresh backend, it will generate a license error even if the license is
set correctly. This happens because the module load happens very late
(in `post_parse_analyze_hook`) but the function call is quite early.

This is fixed by eagerly loading the hypercore handler.

.unreleased/pr_7711

@@ -0,0 +1,2 @@
+Fixes: #7711 License error when using hypercore handler
+Thanks: @jflambert for reporting an bug on license error show in autovacuum

src/cross_module_fn.c

@@ -247,6 +247,24 @@ process_cagg_try_repair(PG_FUNCTION_ARGS)
 	pg_unreachable();
 }
 
+/*
+ * Ensure that the TSL library is loaded before trying to use the handler.
+ *
+ * As for the functions above, the TSL library might not be loaded when this
+ * function is called, so we try to load this function, but fall back on the
+ * Apache error message if not possible.
+ */
+static Datum
+process_hypercore_handler(PG_FUNCTION_ARGS)
+{
+	ts_license_enable_module_loading();
+	if (ts_cm_functions->hypercore_handler != process_hypercore_handler)
+		return ts_cm_functions->hypercore_handler(fcinfo);
+
+	error_no_default_fn_pg_community(fcinfo);
+	pg_unreachable();
+}
+
 static DDLResult
 process_cagg_viewstmt_default(Node *stmt, const char *query_string, void *pstmt,
 							  WithClauseResult *with_clause_options)
@@ -395,7 +413,7 @@ TSDLLEXPORT CrossModuleFunctions ts_cm_functions_default = {
 	.dictionary_compressor_finish = error_no_default_fn_pg_community,
 	.array_compressor_append = error_no_default_fn_pg_community,
 	.array_compressor_finish = error_no_default_fn_pg_community,
-	.hypercore_handler = error_no_default_fn_pg_community,
+	.hypercore_handler = process_hypercore_handler,
 	.hypercore_proxy_handler = error_pg_community_hypercore_proxy_handler,
 	.is_compressed_tid = error_no_default_fn_pg_community,
 

tsl/test/expected/hypercore.out

@@ -784,3 +784,47 @@ select test_hypercore(:'rescan_chunk');
 
 (1 row)
 
+-- Simple test that loading the hypercore handler works on a fresh
+-- backend.
+--
+-- Since TSL library is loaded late (after a query has been executed),
+-- this can generate a license error if an attempt is made to use a
+-- crossmodule function inside a query, and the hypertable handler is
+-- used through GetTableAmRoutine().
+--
+-- To test this, we create a hypercore table, start a fresh
+-- connection, and run a query on it.
+\c :TEST_DBNAME :ROLE_SUPERUSER
+create table crossmodule_test(
+       time timestamptz unique,
+       location int
+);
+select create_hypertable('crossmodule_test', by_range('time', '1d'::interval));
+NOTICE:  adding not-null constraint to column "time"
+ create_hypertable 
+-------------------
+ (7,t)
+(1 row)
+
+select setseed(1);
+ setseed 
+---------
+
+(1 row)
+
+insert into crossmodule_test select t, ceil(random()*10)
+from generate_series('2022-06-01'::timestamptz, '2022-06-10'::timestamptz, '1h') t;
+alter table crossmodule_test
+      set access method hypercore,
+      set (timescaledb.compress_orderby = 'time');
+WARNING:  there was some uncertainty picking the default segment by for the hypertable: You do not have any indexes on columns that can be used for segment_by and thus we are not using segment_by for compression. Please make sure you are not missing any indexes
+NOTICE:  default segment by for hypertable "crossmodule_test" is set to ""
+WARNING:  there was some uncertainty picking the default segment by for the hypertable: You do not have any indexes on columns that can be used for segment_by and thus we are not using segment_by for compression. Please make sure you are not missing any indexes
+NOTICE:  default segment by for hypertable "crossmodule_test" is set to ""
+\c :TEST_DBNAME :ROLE_SUPERUSER
+select count(*) from crossmodule_test;
+ count 
+-------
+   217
+(1 row)
+

tsl/test/sql/hypercore.sql

@@ -427,3 +427,34 @@ returns void as :TSL_MODULE_PATHNAME, 'ts_test_hypercore' language c;
 set role :ROLE_DEFAULT_PERM_USER;
 
 select test_hypercore(:'rescan_chunk');
+
+-- Simple test that loading the hypercore handler works on a fresh
+-- backend.
+--
+-- Since TSL library is loaded late (after a query has been executed),
+-- this can generate a license error if an attempt is made to use a
+-- crossmodule function inside a query, and the hypertable handler is
+-- used through GetTableAmRoutine().
+--
+-- To test this, we create a hypercore table, start a fresh
+-- connection, and run a query on it.
+\c :TEST_DBNAME :ROLE_SUPERUSER
+create table crossmodule_test(
+       time timestamptz unique,
+       location int
+);
+
+select create_hypertable('crossmodule_test', by_range('time', '1d'::interval));
+
+select setseed(1);
+
+insert into crossmodule_test select t, ceil(random()*10)
+from generate_series('2022-06-01'::timestamptz, '2022-06-10'::timestamptz, '1h') t;
+
+alter table crossmodule_test
+      set access method hypercore,
+      set (timescaledb.compress_orderby = 'time');
+
+\c :TEST_DBNAME :ROLE_SUPERUSER
+select count(*) from crossmodule_test;
+