use single row for cursor

bskylink/src/cache/safelinkClient.ts

@@ -227,8 +227,7 @@ export class SafelinkClient {
       const res = await this.db.db
         .selectFrom('safelink_cursor')
         .selectAll()
-        .orderBy('createdAt', 'desc')
+        .where('id', '=', 1)
-        .limit(1)
         .executeTakeFirst()
       if (!res) {
         return ''
@@ -239,13 +238,16 @@ export class SafelinkClient {
   }
 
   private async setCursor(cursor: string) {
+    const updatedAt = new Date()
     try {
       await this.db.db
         .insertInto('safelink_cursor')
         .values({
+          id: 1,
           cursor,
-          createdAt: new Date(),
+          updatedAt,
         })
+        .onConflict(oc => oc.column('id').doUpdateSet({cursor, updatedAt}))
         .execute()
       this.cursor = cursor
     } catch (err) {

bskylink/src/db/migrations/002-safelink.ts

@@ -16,9 +16,9 @@ export async function up(db: Kysely<unknown>): Promise<void> {
 
   await db.schema
     .createTable('safelink_cursor')
-    .addColumn('id', 'bigserial', col => col.primaryKey())
+    .addColumn('id', 'bigserial', col => col.notNull())
     .addColumn('cursor', 'varchar', col => col.notNull())
-    .addColumn('createdAt', 'timestamptz', col => col.notNull())
+    .addColumn('updatedAt', 'timestamptz', col => col.notNull())
     .execute()
 
   await db.schema

bskylink/src/db/schema.ts

@@ -1,4 +1,4 @@
-import {type GeneratedAlways, type Selectable} from 'kysely'
+import {type Selectable} from 'kysely'
 
 export type DbSchema = {
   link: Link
@@ -43,9 +43,9 @@ export interface SafelinkRule {
 }
 
 export interface SafelinkCursor {
-  id: GeneratedAlways<number>
+  id: number
   cursor: string
-  createdAt: Date
+  updatedAt: Date
 }
 
 export type LinkEntry = Selectable<Link>