diff --git a/src/common/backend/parser/gram.y b/src/common/backend/parser/gram.y
index 96e954cd75152557e65b2fdd71261964b2b8e7d0..bc29e008b7bf91344e2770d2a0d09bc36b69216c 100644
--- a/src/common/backend/parser/gram.y
+++ b/src/common/backend/parser/gram.y
@@ -1692,6 +1692,9 @@ UserId:
 							ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("syntax error at or near \"%s\"", $1), parser_errposition(@1)));
 						if (strchr($1,'@'))
 							ereport(ERROR,(errcode(ERRCODE_INVALID_NAME),errmsg("@ can't be allowed in username")));
+						if (strlen($1) >= NAMEDATALEN) {
+							ereport(ERROR,(errcode(ERRCODE_INVALID_NAME),errmsg("String %s is too long for user name (should be no longer than 64)", $1)));
+						}
 						$$ = $1;
 					}
 			| RoleId SET_USER_IDENT
@@ -31352,6 +31355,9 @@ static char* GetValidUserHostId(char* userName, char* hostId)
 	appendStringInfoString(&buf, userName);
 	appendStringInfoString(&buf, "@");
 	appendStringInfoString(&buf, userHostId);
+	if (strlen(buf.data) >= NAMEDATALEN) {
+		ereport(ERROR,(errcode(ERRCODE_INVALID_NAME),errmsg("String %s is too long for user name (should be no longer than 64)", buf.data)));
+	}
 	return buf.data;
 }
 
diff --git a/src/test/regress/input/user_host_test.source b/src/test/regress/input/user_host_test.source
index 12699ddddcb4af0db3c0ef595c40ccfcd6e7f241..e966eef47dddc31a89b3608974ee1402e4c936ab 100644
--- a/src/test/regress/input/user_host_test.source
+++ b/src/test/regress/input/user_host_test.source
@@ -17,6 +17,9 @@ create user 'test_user_host'@'127.0.%' password 'test123@';
 create user 'test_user_host%' password 'test123@';
 create user 'test_user_host'@'127.0.0.1' password 'test123@';
 set b_compatibility_user_host_auth = on;
+CREATE USER 'sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfk vjhsdkfuhc'@'%' PASSWORD 'test123@';
+CREATE USER 'sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfk vjhsdkfuhc' PASSWORD 'test123@';
+CREATE USER sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfkvjhsdkfu@127.0.0.1 PASSWORD 'test123@';
 CREATE USER 'da@localhost'@'%' PASSWORD 'test123@';
 create user if not exists 'test_user_host'@'%' password 'test123@';
 alter user 'test_user_host'@'%' with account lock;
diff --git a/src/test/regress/output/user_host_test.source b/src/test/regress/output/user_host_test.source
index a150e999c06ad1a38b92ecc924c28b3cd3342fa1..fe89b8201cc2eaf554c209f243fd48f6c06f164c 100644
--- a/src/test/regress/output/user_host_test.source
+++ b/src/test/regress/output/user_host_test.source
@@ -48,6 +48,13 @@ LINE 1: create user 'test_user_host%' password 'test123@';
 create user 'test_user_host'@'127.0.0.1' password 'test123@';
 ERROR:  user@host is only supported in b database when the b_compatibility_user_host_auth is on
 set b_compatibility_user_host_auth = on;
+CREATE USER 'sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfk vjhsdkfuhc'@'%' PASSWORD 'test123@';
+ERROR:  String sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfk vjhsdkfuhc@% is too long for user name (should be no longer than 64)
+CREATE USER 'sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfk vjhsdkfuhc' PASSWORD 'test123@';
+ERROR:  String sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfk vjhsdkfuhc is too long for user name (should be no longer than 64)
+CREATE USER sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfkvjhsdkfu@127.0.0.1 PASSWORD 'test123@';
+NOTICE:  identifier "sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfkvjhsdkfu" will be truncated to "sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfkvjhsdk"
+ERROR:  String sssssssssssssskkdcjhshfedrfbberfheurfhefhhdfjdfhkdfjshdfkvjhsdk@127.0.0.1 is too long for user name (should be no longer than 64)
 CREATE USER 'da@localhost'@'%' PASSWORD 'test123@';
 ERROR:  @ can't be allowed in username
 create user if not exists 'test_user_host'@'%' password 'test123@';