feat: support shared tenant database sharding

server/internal/library/imtenant/db.go

@@ -23,7 +23,7 @@ const registryDbGroup = "imRegistry"
 
 var registryDbGroupOnce sync.Once
 
-// DB resolves a tenant registry record and returns the corresponding business DB.
+// DB resolves a tenant registry record and returns the shared IM business DB.
 func DB(ctx context.Context, tenantId int64) (db gdb.DB, tenant *entity.ImTenant, err error) {
 	if tenantId <= 0 {
 		return nil, nil, gerror.New("租户ID不能为空")
@@ -36,27 +36,48 @@ func DB(ctx context.Context, tenantId int64) (db gdb.DB, tenant *entity.ImTenant
 		return nil, nil, gerror.New("租户不存在")
 	}
 
-	link, err := tenantLink(ctx, tenant)
+	db, err = SharedDB(ctx)
 	if err != nil {
 		return nil, nil, err
 	}
+	return db, tenant, nil
+}
 
-	group := fmt.Sprintf("im_tenant_%d_%x", tenant.Id, hash(link))
+// SharedDB returns the common IM database configured by the default tenant.
+// Tenant isolation inside this database is implemented by tenant_id predicates
+// and the three tenant-partitioned high-volume table families.
+func SharedDB(ctx context.Context) (gdb.DB, error) {
+	var sharedTenant *entity.ImTenant
+	if err := RegistryDB().Model(dao.ImTenant.Table()).Safe().Ctx(ctx).
+		Where(dao.ImTenant.Columns().Code, "default").Scan(&sharedTenant); err != nil {
+		return nil, gerror.Wrap(err, "获取共享业务库配置失败")
+	}
+	if sharedTenant == nil || sharedTenant.Id <= 0 {
+		return nil, gerror.New("默认商户不存在，无法确定共享业务库")
+	}
+	link, err := tenantLink(ctx, sharedTenant)
+	if err != nil {
+		return nil, err
+	}
+	return dbForLink(link, sharedTenant.Id)
+}
+
+func dbForLink(link string, ownerID int64) (gdb.DB, error) {
+	group := fmt.Sprintf("im_shared_%d_%x", ownerID, hash(link))
 	if cached, ok := tenantDbGroups.Load(group); ok && cached == link {
-		db, err = gdb.Instance(group)
-		return db, tenant, err
+		return gdb.Instance(group)
 	}
 
-	if err = gdb.SetConfigGroup(group, gdb.ConfigGroup{{Link: link}}); err != nil {
-		return nil, nil, gerror.Wrap(err, "初始化租户业务库连接失败")
+	if err := gdb.SetConfigGroup(group, gdb.ConfigGroup{{Link: link}}); err != nil {
+		return nil, gerror.Wrap(err, "初始化共享业务库连接失败")
 	}
 	tenantDbGroups.Store(group, link)
 
-	db, err = gdb.Instance(group)
+	db, err := gdb.Instance(group)
 	if err != nil {
-		return nil, nil, gerror.Wrap(err, "获取租户业务库连接失败")
+		return nil, gerror.Wrap(err, "获取共享业务库连接失败")
 	}
-	return db, tenant, nil
+	return db, nil
 }
 
 // RegistryDB returns the dedicated tenant registry connection, or the default