Add opt-in slow SQL and database diagnostics

src/lib/server/db/index.ts

@@ -10,6 +10,7 @@ import { backfillLeaderboard } from '../fleet/leaderboard-ingest.js';
 import { initializeFleetSettings } from './fleet-settings.js';
 import { migrateServerHistory } from './server-history.js';
 import { migrateNativeInstances } from '../backends/schema.js';
+import { timeStatement } from './slow-statements.js';
 
 let _db: Database.Database | null = null;
 
@@ -414,11 +415,12 @@ export function db(): Database.Database {
     // Callers share statement options (e.g. raw()); use consistent options for
     // identical SQL and pass values to run/get/all rather than binding permanently.
     const statements = new Map<string, Database.Statement>();
+    const slowMs = Number(process.env.EC_SLOW_SQL_MS ?? 0);
     const prepare = handle.prepare.bind(handle);
     handle.prepare = ((sql: string) => {
         let statement = statements.get(sql);
         if (!statement) {
-            statement = prepare(sql);
+            statement = timeStatement(prepare(sql), sql, slowMs);
             statements.set(sql, statement);
         }
         return statement;

src/lib/server/db/slow-statements.ts

@@ -0,0 +1,19 @@
+import type Database from 'better-sqlite3';
+
+/** Log query shapes, never bound values or SQL string literals. Disabled by default. */
+export function timeStatement(statement: Database.Statement, sql: string, thresholdMs: number): Database.Statement {
+    if (!Number.isFinite(thresholdMs) || thresholdMs <= 0) return statement;
+    const shape = sql.replace(/'(?:''|[^'])*'/g, '?').replace(/\s+/g, ' ').trim().slice(0, 200);
+    for (const method of ['run', 'get', 'all'] as const) {
+        const original = statement[method].bind(statement) as (...args: unknown[]) => unknown;
+        Object.defineProperty(statement, method, { value: (...args: unknown[]) => {
+            const started = performance.now();
+            try { return original(...args); }
+            finally {
+                const ms = performance.now() - started;
+                if (ms >= thresholdMs) console.warn('[sql]', { ms: Math.round(ms), method, sql: shape });
+            }
+        } });
+    }
+    return statement;
+}