BABEL: Handling babelfish specific GUC after commit a1a00b3 (babelfis…

…h-for-postgresql#290)

With commit a1a00b3, community refactored the code related to GUC handling
and introduced certain optimisation around GUC handling. For example, they have introduced following three fields for various purpose --

static dlist_head guc_nondef_list;	/* list of variables that have source
									 * different from PGC_S_DEFAULT */
static slist_head guc_stack_list;	/* list of variables that have non-NULL
									 * stack */
static slist_head guc_report_list;	/* list of variables that have the
									 * GUC_NEEDS_REPORT bit set in status */

These all fields are getting updated based on various operations on the GUC. Field guc_nondef_list is to track non-default
value of various GUCs and is updated through helper function set_guc_source(...). Now the logic of Babelfish GUC
handling is somewhat different and was not updated to accommodate these code changes. This resulted in hang while
communicating GUCs with non-default value to parallel worker.

This commit aims to fix that issue by providing wrapper around set_guc_source(...) so that Babelfish side can utilise it to
update the guc_nondef_list stack appropriately.

Extension PR: babelfish-for-postgresql/babelfish_extensions#2244
Task: BABEL-4668, BABEL-4669, BABEL-4670, BABEL-4671
Signed-off-by: Dipesh Dhameliya <[email protected]>

src/backend/utils/misc/guc.c

@@ -6808,3 +6808,9 @@ guc_set_stack_value(struct config_generic *gconf, config_var_value *val)
 {
 	set_stack_value(gconf,  val);
 }
+
+void
+babelfish_set_guc_source(struct config_generic *gconf, GucSource newsource)
+{
+	set_guc_source(gconf, newsource);
+}

src/include/utils/guc_tables.h

@@ -320,4 +320,6 @@ extern PGDLLEXPORT guc_push_old_value_hook_type guc_push_old_value_hook;
 typedef			void(*validate_set_config_function_hook_type) (char *name, char *value);
 extern PGDLLEXPORT validate_set_config_function_hook_type validate_set_config_function_hook;
 
+extern void babelfish_set_guc_source(struct config_generic *gconf, GucSource newsource);
+
 #endif							/* GUC_TABLES_H */