br: fix pitr system table inconsistency issue

br/pkg/stream/rewrite_meta_rawkv.go

@@ -227,7 +227,9 @@ func (sr *SchemasReplace) rewriteKeyForTable(
 	if !exist {
 		return nil, errors.Annotatef(berrors.ErrInvalidArgument, "failed to find table id:%v in maps", tableID)
 	}
-	if tableReplace.FilteredOut {
+
+	// don't restore meta kv change for system db, not supported yet
+	if tableReplace.FilteredOut || utils.IsSysOrTempSysDB(dbReplace.Name) {
 		return nil, nil
 	}
 

br/pkg/stream/table_mapping.go

@@ -293,11 +293,29 @@ func (tm *TableMappingManager) MergeBaseDBReplace(baseMap map[UpstreamID]*DBRepl
 			existingDBReplace.DbID = newID
 		}
 
+		// db replace in `TableMappingManager` has no name yet, it is determined by baseMap.
+		// TODO: update the name of the db replace that is not exists in baseMap. Now it is OK because user tables' name is not used.
+		if existingDBReplace.Name == "" {
+			if baseDBReplace, exists := baseMap[upDBID]; exists && baseDBReplace.Name != "" {
+				existingDBReplace.Name = baseDBReplace.Name
+			}
+		}
+
 		for upTableID, existingTableReplace := range existingDBReplace.TableMap {
 			if newID, exists := tm.globalIdMap[upTableID]; exists {
 				existingTableReplace.TableID = newID
 			}
 
+			// table replace in `TableMappingManager` has no name yet, it is determined by baseMap.
+			// TODO: update the name of the table replace that is not exists in baseMap. Now it is OK because user tables' name is not used.
+			if existingTableReplace.Name == "" {
+				if baseDBReplace, dbExists := baseMap[upDBID]; dbExists {
+					if baseTableReplace, tableExists := baseDBReplace.TableMap[upTableID]; tableExists && baseTableReplace.Name != "" {
+						existingTableReplace.Name = baseTableReplace.Name
+					}
+				}
+			}
+
 			for partUpID := range existingTableReplace.PartitionMap {
 				if newID, exists := tm.globalIdMap[partUpID]; exists {
 					existingTableReplace.PartitionMap[partUpID] = newID

br/pkg/task/stream.go

@@ -1944,7 +1944,7 @@ func buildRewriteRules(schemasReplace *stream.SchemasReplace) map[int64]*restore
 	rules := make(map[int64]*restoreutils.RewriteRules)
 
 	for _, dbReplace := range schemasReplace.DbReplaceMap {
-		if dbReplace.FilteredOut {
+		if dbReplace.FilteredOut || utils.IsSysOrTempSysDB(dbReplace.Name) {
 			continue
 		}
 		for oldTableID, tableReplace := range dbReplace.TableMap {

br/pkg/utils/schema.go

@@ -55,6 +55,14 @@ func StripTempDBPrefixIfNeeded(tempDB string) (string, bool) {
 	return tempDB[len(temporaryDBNamePrefix):], true
 }
 
+// IsSysOrTempSysDB tests whether the database is system DB or prefixed with temp.
+func IsSysOrTempSysDB(db string) bool {
+	if name, ok := StripTempDBPrefixIfNeeded(db); IsSysDB(name) && ok {
+		return true
+	}
+	return false
+}
+
 // GetSysDBCIStrName get the CIStr name of system DB
 func GetSysDBCIStrName(tempDB ast.CIStr) (ast.CIStr, bool) {
 	if ok := strings.HasPrefix(tempDB.O, temporaryDBNamePrefix); !ok {

br/tests/br_pitr_table_filter/run.sh

@@ -450,25 +450,53 @@ test_system_tables() {
     run_sql "create schema $DB;"
 
     echo "write initial data and do snapshot backup"
-    # create and populate a user table for reference
-    run_sql "create table $DB.user_table(id int primary key);"
-    run_sql "insert into $DB.user_table values (1);"
-
     # make some changes to system tables
     run_sql "create user 'test_user'@'%' identified by 'password';"
     run_sql "grant select on $DB.* to 'test_user'@'%';"
 
     run_br backup full -s "local://$TEST_DIR/$TASK_NAME/full" --pd $PD_ADDR
 
     echo "make more changes to system tables and wait for log backup"
-    run_sql "revoke select on $DB.* from 'test_user'@'%';"
-    run_sql "grant insert on $DB.* to 'test_user'@'%';"
+    run_sql "create user 'post_backup_user'@'%' identified by 'otherpassword';"
     run_sql "alter user 'test_user'@'%' identified by 'newpassword';"
 
     . "$CUR/../br_test_utils.sh" && wait_log_checkpoint_advance "$TASK_NAME"
 
     restart_services || { echo "Failed to restart services"; exit 1; }
 
+    echo "Test 1: Verify that default restore behavior (no filter) properly handles system tables"
+    # restore without any filter, should only restore snapshot system tables, not log backup.
+    # this is the current behavior as restore log backup to system table will have issue
+    run_br --pd "$PD_ADDR" restore point -s "local://$TEST_DIR/$TASK_NAME/log" --full-backup-storage "local://$TEST_DIR/$TASK_NAME/full"
+
+
+    # verify system tables are restored from snapshot only
+    # only test_user should exist, post_backup_user should not exist
+    users_result=$(run_sql "SELECT _tidb_rowid, user, host, authentication_string FROM mysql.user WHERE user IN ('test_user', 'post_backup_user')")
+
+    test_user_count=$(echo "$users_result" | grep -c "test_user" || true)
+
+    # Verify there is exactly one test_user
+    if [ "$test_user_count" -eq 0 ]; then
+        echo "Error: test_user not found in mysql.user table"
+        exit 1
+    elif [ "$test_user_count" -gt 1 ]; then
+        echo "Error: Found $test_user_count instances of test_user in mysql.user table, expected exactly 1"
+        echo "Full query result:"
+        echo "$users_result"
+        exit 1
+    fi
+
+    # Check that post_backup_user does not exist (was created after snapshot)
+    if echo "$users_result" | grep -q "post_backup_user"; then
+        echo "Error: post_backup_user found in mysql.user table but should not be restored"
+        echo "Full query result:"
+        echo "$users_result"
+        exit 1
+    fi
+
+    echo "Default restore correctly restored system tables from snapshot only: verified one test_user exists"
+
     echo "PiTR should error out when system tables are included with explicit filter"
     restore_fail=0
     run_br --pd "$PD_ADDR" restore point -f "*.*" -s "local://$TEST_DIR/$TASK_NAME/log" --full-backup-storage "local://$TEST_DIR/$TASK_NAME/full" || restore_fail=1