chore: import upstream snapshot with attribution

apps/sim/lib/table/tx.ts

@@ -0,0 +1,50 @@
+/**
+ * Shared transaction / locking helpers for the table service layer.
+ *
+ * Internal module: not exposed via the `@/lib/table` barrel. Consumers import
+ * directly from `@/lib/table/tx`.
+ */
+
+import { sql } from 'drizzle-orm'
+import type { DbTransaction } from '@/lib/table/planner'
+
+const TIMEOUT_CAP_MS = 10 * 60_000
+
+/**
+ * Sets per-transaction Postgres timeouts via `SET LOCAL`.
+ *
+ * `lock_timeout` is the critical one: without it, a waiter inherits the full
+ * `statement_timeout` clock, so one stuck writer can drain the pool.
+ *
+ * Safe under pgBouncer transaction pooling — `SET LOCAL` is transaction-scoped
+ * and cleared at COMMIT/ROLLBACK before the session returns to the pool.
+ */
+export async function setTableTxTimeouts(
+  trx: DbTransaction,
+  opts?: { statementMs?: number; lockMs?: number; idleMs?: number }
+) {
+  const s = opts?.statementMs ?? 10_000
+  const l = opts?.lockMs ?? 3_000
+  const i = opts?.idleMs ?? 5_000
+  await trx.execute(sql.raw(`SET LOCAL statement_timeout = '${s}ms'`))
+  await trx.execute(sql.raw(`SET LOCAL lock_timeout = '${l}ms'`))
+  await trx.execute(sql.raw(`SET LOCAL idle_in_transaction_session_timeout = '${i}ms'`))
+}
+
+/**
+ * Scales `statement_timeout` to the expected row-count work.
+ *
+ * Bulk operations that rewrite JSONB or cascade row triggers (e.g.
+ * `replaceTableRows`, `deleteColumn`, `renameColumn`) scale roughly linearly
+ * with row count. A fixed cap would regress large-table users who never saw a
+ * timeout before `SET LOCAL` was introduced. This helper picks
+ * `max(baseMs, rowCount * perRowMs)`, capped at 10 minutes so a single
+ * runaway transaction cannot indefinitely pin a pool connection.
+ */
+export function scaledStatementTimeoutMs(
+  rowCount: number,
+  opts: { baseMs: number; perRowMs: number }
+): number {
+  const safeRowCount = Math.max(0, rowCount)
+  return Math.min(TIMEOUT_CAP_MS, Math.max(opts.baseMs, safeRowCount * opts.perRowMs))
+}