fix(pipeline): fix priority

- The newly introduced priority field is set to NULL by default, which
causes pre-existing pipelines to crash devlake when starting after a
version upgrade.

Author: Kostas Petrakis

backend/core/models/migrationscripts/20251022_fix_null_priority.go

@@ -0,0 +1,67 @@
+/*
+Licensed to the Apache Software Foundation (ASF) under one or more
+contributor license agreements.  See the NOTICE file distributed with
+this work for additional information regarding copyright ownership.
+The ASF licenses this file to You under the Apache License, Version 2.0
+(the "License"); you may not use this file except in compliance with
+the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package migrationscripts
+
+import (
+	"github.com/apache/incubator-devlake/core/context"
+	"github.com/apache/incubator-devlake/core/dal"
+	"github.com/apache/incubator-devlake/core/errors"
+	"github.com/apache/incubator-devlake/core/plugin"
+)
+
+var _ plugin.MigrationScript = (*fixNullPriority)(nil)
+
+type fixNullPriority struct{}
+
+type blueprint20251022 struct {
+	Priority int `json:"priority"`
+}
+
+func (blueprint20251022) TableName() string {
+	return "_devlake_blueprints"
+}
+
+type pipeline20251022 struct {
+	Priority int `json:"priority"`
+}
+
+func (pipeline20251022) TableName() string {
+	return "_devlake_pipelines"
+}
+
+func (*fixNullPriority) Up(basicRes context.BasicRes) errors.Error {
+	// Set default value 0 for NULL priority values in existing rows
+	db := basicRes.GetDal()
+	err := db.UpdateColumn(&blueprint20251022{}, "priority", 0, dal.Where("priority IS NULL"))
+	if err != nil {
+		return err
+	}
+	err = db.UpdateColumn(&pipeline20251022{}, "priority", 0, dal.Where("priority IS NULL"))
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (*fixNullPriority) Version() uint64 {
+	return 20251022195645
+}
+
+func (*fixNullPriority) Name() string {
+	return "fix null priority values in blueprints and pipelines"
+}

backend/core/models/migrationscripts/register.go

@@ -140,5 +140,6 @@ func All() []plugin.MigrationScript {
 		new(extendFieldSizeForCq),
 		new(addIssueFixVerion),
 		new(addPipelinePriority),
+		new(fixNullPriority),
 	}
 }