From 78a6de18ce831e53a85cc525dd59294207e38721 Mon Sep 17 00:00:00 2001
From: zhangwenchao <656540940@qq.com>
Date: Thu, 23 Nov 2023 10:39:47 +0800
Subject: [PATCH] Judge whether commands need to be dispatched to QEs in QD

---
 src/backend/utils/misc/guc.c | 60 +++++++++++++++++++++++++++---------
 1 file changed, 46 insertions(+), 14 deletions(-)

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index e9881d2bc7d..6b0f9548101 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -252,6 +252,7 @@ static double defunct_double = 0;
 static ConfigVariable *ProcessConfigFileInternal(GucContext context,
 												 bool applySettings, int elevel);
 
+static bool CdbDoesNeedDispatchCommand(VariableSetStmt *stmt);
 
 /*
  * Options for enum values defined in this module.
@@ -8943,7 +8944,9 @@ void
 ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
 {
 	GucAction	action = stmt->is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET;
+	bool		need_dispatch = false;
 
+	need_dispatch = CdbDoesNeedDispatchCommand(stmt);
 	/*
 	 * Workers synchronize these parameters at the start of the parallel
 	 * operation; then, we block SET during the operation.
@@ -8969,7 +8972,8 @@ ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
 									 (superuser() ? PGC_SUSET : PGC_USERSET),
 									 PGC_S_SESSION,
 									 action, true, 0, false);
-			DispatchSetPGVariable(stmt->name, stmt->args, stmt->is_local);
+			if (need_dispatch)
+				DispatchSetPGVariable(stmt->name, stmt->args, stmt->is_local);
 			break;
 		case VAR_SET_MULTI:
 
@@ -8992,14 +8996,14 @@ ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
 					DefElem    *item = (DefElem *) lfirst(head);
 
 					if (strcmp(item->defname, "transaction_isolation") == 0)
-						SetPGVariable("transaction_isolation",
-									  list_make1(item->arg), stmt->is_local);
+						SetPGVariableOptDispatch("transaction_isolation",
+									  list_make1(item->arg), stmt->is_local, need_dispatch);
 					else if (strcmp(item->defname, "transaction_read_only") == 0)
-						SetPGVariable("transaction_read_only",
-									  list_make1(item->arg), stmt->is_local);
+						SetPGVariableOptDispatch("transaction_read_only",
+									  list_make1(item->arg), stmt->is_local, need_dispatch);
 					else if (strcmp(item->defname, "transaction_deferrable") == 0)
-						SetPGVariable("transaction_deferrable",
-									  list_make1(item->arg), stmt->is_local);
+						SetPGVariableOptDispatch("transaction_deferrable",
+									  list_make1(item->arg), stmt->is_local, need_dispatch);
 					else
 						elog(ERROR, "unexpected SET TRANSACTION element: %s",
 							 item->defname);
@@ -9014,14 +9018,14 @@ ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
 					DefElem    *item = (DefElem *) lfirst(head);
 
 					if (strcmp(item->defname, "transaction_isolation") == 0)
-						SetPGVariable("default_transaction_isolation",
-									  list_make1(item->arg), stmt->is_local);
+						SetPGVariableOptDispatch("default_transaction_isolation",
+									  list_make1(item->arg), stmt->is_local, need_dispatch);
 					else if (strcmp(item->defname, "transaction_read_only") == 0)
-						SetPGVariable("default_transaction_read_only",
-									  list_make1(item->arg), stmt->is_local);
+						SetPGVariableOptDispatch("default_transaction_read_only",
+									  list_make1(item->arg), stmt->is_local, need_dispatch);
 					else if (strcmp(item->defname, "transaction_deferrable") == 0)
-						SetPGVariable("default_transaction_deferrable",
-									  list_make1(item->arg), stmt->is_local);
+						SetPGVariableOptDispatch("default_transaction_deferrable",
+									  list_make1(item->arg), stmt->is_local, need_dispatch);
 					else
 						elog(ERROR, "unexpected SET SESSION element: %s",
 							 item->defname);
@@ -9069,7 +9073,7 @@ ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
 		stmt->kind == VAR_RESET ||
 		stmt->kind == VAR_RESET_ALL)
 	{
-		if (Gp_role == GP_ROLE_DISPATCH)
+		if (Gp_role == GP_ROLE_DISPATCH && need_dispatch)
 		{
 			/*
 			 * RESET must be dispatched different, because it can't
@@ -13020,4 +13024,32 @@ check_default_with_oids(bool *newval, void **extra, GucSource source)
 	return true;
 }
 
+static bool
+CdbDoesNeedDispatchCommand(VariableSetStmt *stmt)
+{
+	bool need_dispatch = true;
+
+	switch (stmt->kind)
+	{
+		case VAR_SET_VALUE:
+		case VAR_SET_CURRENT:
+		case VAR_SET_DEFAULT:
+			if (strcmp(stmt->name, "hashdata.warehouse") == 0)
+				need_dispatch = false;
+			break;
+		case VAR_SET_MULTI:
+			if (strcmp(stmt->name, "TRANSACTION") == 0)
+				need_dispatch = false;
+			else if (strcmp(stmt->name, "SESSION CHARACTERISTICS") == 0)
+				need_dispatch = false;
+			else if ((strcmp(stmt->name, "TRANSACTION SNAPSHOT") == 0))
+				need_dispatch = false;
+			break;
+		default:
+			break;
+	}
+
+	return need_dispatch;
+}
+
 #include "guc-file.c"