Transform proconfig for faster execution.

Store function config settings in lists to avoid the need to parse and
allocate for each function execution.

Speedup is modest but significant. Additionally, this change also
seems cleaner and supports some other performance improvements under
discussion.

Discussion: https://postgr.es/m/04c8592dbd694e4114a3ed87139a7a04e4363030.camel@j-davis.com
Reviewed-by: Nathan Bossart

src/backend/utils/fmgr/fmgr.c

@@ -612,7 +612,8 @@ struct fmgr_security_definer_cache
 {
 	FmgrInfo	flinfo;			/* lookup info for target function */
 	Oid			userid;			/* userid to set, or InvalidOid */
-	ArrayType  *proconfig;		/* GUC values to set, or NULL */
+	List	   *configNames;	/* GUC names to set, or NIL */
+	List	   *configValues;	/* GUC values to set, or NIL */
 	Datum		arg;			/* passthrough argument for plugin modules */
 };
 
@@ -634,6 +635,8 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 	FmgrInfo   *save_flinfo;
 	Oid			save_userid;
 	int			save_sec_context;
+	ListCell   *lc1;
+	ListCell   *lc2;
 	volatile int save_nestlevel;
 	PgStat_FunctionCallUsage fcusage;
 
@@ -666,8 +669,11 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 								&isnull);
 		if (!isnull)
 		{
+			ArrayType *array;
 			oldcxt = MemoryContextSwitchTo(fcinfo->flinfo->fn_mcxt);
-			fcache->proconfig = DatumGetArrayTypePCopy(datum);
+			array = DatumGetArrayTypeP(datum);
+			TransformGUCArray(array, &fcache->configNames,
+							  &fcache->configValues);
 			MemoryContextSwitchTo(oldcxt);
 		}
 
@@ -680,7 +686,7 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 
 	/* GetUserIdAndSecContext is cheap enough that no harm in a wasted call */
 	GetUserIdAndSecContext(&save_userid, &save_sec_context);
-	if (fcache->proconfig)		/* Need a new GUC nesting level */
+	if (fcache->configNames != NIL)		/* Need a new GUC nesting level */
 		save_nestlevel = NewGUCNestLevel();
 	else
 		save_nestlevel = 0;		/* keep compiler quiet */
@@ -689,12 +695,17 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 		SetUserIdAndSecContext(fcache->userid,
 							   save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
 
-	if (fcache->proconfig)
+	forboth(lc1, fcache->configNames, lc2, fcache->configValues)
 	{
-		ProcessGUCArray(fcache->proconfig,
-						(superuser() ? PGC_SUSET : PGC_USERSET),
-						PGC_S_SESSION,
-						GUC_ACTION_SAVE);
+		GucContext	 context = superuser() ? PGC_SUSET : PGC_USERSET;
+		GucSource	 source	 = PGC_S_SESSION;
+		GucAction	 action	 = GUC_ACTION_SAVE;
+		char		*name	 = lfirst(lc1);
+		char		*value	 = lfirst(lc2);
+
+		(void) set_config_option(name, value,
+								 context, source,
+								 action, true, 0, false);
 	}
 
 	/* function manager hook */
@@ -737,7 +748,7 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 
 	fcinfo->flinfo = save_flinfo;
 
-	if (fcache->proconfig)
+	if (fcache->configNames != NIL)
 		AtEOXact_GUC(true, save_nestlevel);
 	if (OidIsValid(fcache->userid))
 		SetUserIdAndSecContext(save_userid, save_sec_context);

src/backend/utils/misc/guc.c

@@ -6215,14 +6215,12 @@ ParseLongOption(const char *string, char **name, char **value)
 
 
 /*
- * Handle options fetched from pg_db_role_setting.setconfig,
- * pg_proc.proconfig, etc.  Caller must specify proper context/source/action.
- *
- * The array parameter must be an array of TEXT (it must not be NULL).
+ * Transform array of GUC settings into lists of names and values. The lists
+ * are faster to process in cases where the settings must be applied
+ * repeatedly (e.g. for each function invocation).
  */
 void
-ProcessGUCArray(ArrayType *array,
-				GucContext context, GucSource source, GucAction action)
+TransformGUCArray(ArrayType *array, List **names, List **values)
 {
 	int			i;
 
@@ -6231,6 +6229,8 @@ ProcessGUCArray(ArrayType *array,
 	Assert(ARR_NDIM(array) == 1);
 	Assert(ARR_LBOUND(array)[0] == 1);
 
+	*names = NIL;
+	*values = NIL;
 	for (i = 1; i <= ARR_DIMS(array)[0]; i++)
 	{
 		Datum		d;
@@ -6262,14 +6262,45 @@ ProcessGUCArray(ArrayType *array,
 			continue;
 		}
 
+		*names = lappend(*names, name);
+		*values = lappend(*values, value);
+
+		pfree(s);
+	}
+}
+
+
+/*
+ * Handle options fetched from pg_db_role_setting.setconfig,
+ * pg_proc.proconfig, etc.  Caller must specify proper context/source/action.
+ *
+ * The array parameter must be an array of TEXT (it must not be NULL).
+ */
+void
+ProcessGUCArray(ArrayType *array,
+				GucContext context, GucSource source, GucAction action)
+{
+	List *gucNames;
+	List *gucValues;
+	ListCell *lc1;
+	ListCell *lc2;
+
+	TransformGUCArray(array, &gucNames, &gucValues);
+	forboth(lc1, gucNames, lc2, gucValues)
+	{
+		char *name = lfirst(lc1);
+		char *value = lfirst(lc2);
+
 		(void) set_config_option(name, value,
 								 context, source,
 								 action, true, 0, false);
 
 		pfree(name);
 		pfree(value);
-		pfree(s);
 	}
+
+	list_free(gucNames);
+	list_free(gucValues);
 }
 
 

src/include/utils/guc.h

@@ -391,6 +391,8 @@ extern void AlterSystemSetConfigFile(AlterSystemStmt *altersysstmt);
 extern char *GetConfigOptionByName(const char *name, const char **varname,
 								   bool missing_ok);
 
+extern void TransformGUCArray(ArrayType *array, List **configNames,
+							  List **configValues);
 extern void ProcessGUCArray(ArrayType *array,
 							GucContext context, GucSource source, GucAction action);
 extern ArrayType *GUCArrayAdd(ArrayType *array, const char *name, const char *value);