Add infrastructure to save and restore GUC values.

This is further infrastructure for parallelism.

Amit Khandekar, Noah Misch, Robert Haas

contrib/dblink/dblink.c

@@ -2980,7 +2980,7 @@ applyRemoteGucs(PGconn *conn)
 		/* Apply the option (this will throw error on failure) */
 		(void) set_config_option(gucName, remoteVal,
 								 PGC_USERSET, PGC_S_SESSION,
-								 GUC_ACTION_SAVE, true, 0);
+								 GUC_ACTION_SAVE, true, 0, false);
 	}
 
 	return nestlevel;

contrib/postgres_fdw/postgres_fdw.c

@@ -2104,15 +2104,15 @@ set_transmission_modes(void)
 	if (DateStyle != USE_ISO_DATES)
 		(void) set_config_option("datestyle", "ISO",
 								 PGC_USERSET, PGC_S_SESSION,
-								 GUC_ACTION_SAVE, true, 0);
+								 GUC_ACTION_SAVE, true, 0, false);
 	if (IntervalStyle != INTSTYLE_POSTGRES)
 		(void) set_config_option("intervalstyle", "postgres",
 								 PGC_USERSET, PGC_S_SESSION,
-								 GUC_ACTION_SAVE, true, 0);
+								 GUC_ACTION_SAVE, true, 0, false);
 	if (extra_float_digits < 3)
 		(void) set_config_option("extra_float_digits", "3",
 								 PGC_USERSET, PGC_S_SESSION,
-								 GUC_ACTION_SAVE, true, 0);
+								 GUC_ACTION_SAVE, true, 0, false);
 
 	return nestlevel;
 }

src/backend/commands/extension.c

@@ -814,11 +814,11 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 	if (client_min_messages < WARNING)
 		(void) set_config_option("client_min_messages", "warning",
 								 PGC_USERSET, PGC_S_SESSION,
-								 GUC_ACTION_SAVE, true, 0);
+								 GUC_ACTION_SAVE, true, 0, false);
 	if (log_min_messages < WARNING)
 		(void) set_config_option("log_min_messages", "warning",
 								 PGC_SUSET, PGC_S_SESSION,
-								 GUC_ACTION_SAVE, true, 0);
+								 GUC_ACTION_SAVE, true, 0, false);
 
 	/*
 	 * Set up the search path to contain the target schema, then the schemas
@@ -843,7 +843,7 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 
 	(void) set_config_option("search_path", pathbuf.data,
 							 PGC_USERSET, PGC_S_SESSION,
-							 GUC_ACTION_SAVE, true, 0);
+							 GUC_ACTION_SAVE, true, 0, false);
 
 	/*
 	 * Set creating_extension and related variables so that

src/backend/utils/adt/ri_triggers.c

@@ -2422,7 +2422,7 @@ RI_Initial_Check(Trigger *trigger, Relation fk_rel, Relation pk_rel)
 	snprintf(workmembuf, sizeof(workmembuf), "%d", maintenance_work_mem);
 	(void) set_config_option("work_mem", workmembuf,
 							 PGC_USERSET, PGC_S_SESSION,
-							 GUC_ACTION_SAVE, true, 0);
+							 GUC_ACTION_SAVE, true, 0, false);
 
 	if (SPI_connect() != SPI_OK_CONNECT)
 		elog(ERROR, "SPI_connect failed");

src/backend/utils/misc/guc-file.l

@@ -318,7 +318,7 @@ ProcessConfigFile(GucContext context)
 		/* Now we can re-apply the wired-in default (i.e., the boot_val) */
 		if (set_config_option(gconf->name, NULL,
 							  context, PGC_S_DEFAULT,
-							  GUC_ACTION_SET, true, 0) > 0)
+							  GUC_ACTION_SET, true, 0, false) > 0)
 		{
 			/* Log the change if appropriate */
 			if (context == PGC_SIGHUP)
@@ -373,7 +373,7 @@ ProcessConfigFile(GucContext context)
 
 		scres = set_config_option(item->name, item->value,
 								  context, PGC_S_FILE,
-								  GUC_ACTION_SET, true, 0);
+								  GUC_ACTION_SET, true, 0, false);
 		if (scres > 0)
 		{
 			/* variable was updated, so log the change if appropriate */

src/include/utils/guc.h

@@ -339,7 +339,8 @@ extern bool parse_int(const char *value, int *result, int flags,
 extern bool parse_real(const char *value, double *result);
 extern int set_config_option(const char *name, const char *value,
 				  GucContext context, GucSource source,
-				  GucAction action, bool changeVal, int elevel);
+				  GucAction action, bool changeVal, int elevel,
+				  bool is_reload);
 extern void AlterSystemSetConfigFile(AlterSystemStmt *setstmt);
 extern char *GetConfigOptionByName(const char *name, const char **varname);
 extern void GetConfigOptionByNum(int varnum, const char **values, bool *noshow);
@@ -363,6 +364,11 @@ extern void write_nondefault_variables(GucContext context);
 extern void read_nondefault_variables(void);
 #endif
 
+/* GUC serialization */
+extern Size EstimateGUCStateSpace(void);
+extern void SerializeGUCState(Size maxsize, char *start_address);
+extern void RestoreGUCState(void *gucstate);
+
 /* Support for messages reported from GUC check hooks */
 
 extern PGDLLIMPORT char *GUC_check_errmsg_string;