Use select-for-update to make sure board compaction is not run while …

…loading board

No strong reason to suppose this concurrency would be harmful
but the opposite isn't proven either so better safe than sorry.

backend/src/board-store.ts

@@ -29,7 +29,7 @@ with allow_lists as (
  from board_access a
  where a.board_id = b.id
  ) as allow_list
- from board b
+ from board b for update
 )
 select id,
  jsonb_set (content - 'accessPolicy', '{accessPolicy}', cast(case when allow_list is null then 'null' else (json_build_object('allowList', allow_list, 'publicRead', public_read, 'publicWrite', public_write)) end as jsonb)) as content

backend/src/compact-history.ts

@@ -15,10 +15,13 @@ import {
  verifyContinuityFromMetas,
 } from "./board-store"
 import { inTransaction } from "./db"
+import { sleep } from "../../common/src/sleep"
 
 export async function quickCompactBoardHistory(id: Id) {
  let fallback = false
  const result = inTransaction(async (client) => {
+ // Lock the board to prevent loading the board while compacting
+ await client.query("select 1 from board where id=$1 for update", [id])
  const bundleMetas = await getBoardHistoryBundleMetas(client, id)
  if (bundleMetas.length === 0) return
  const consistent = verifyContinuityFromMetas(id, 0, bundleMetas)