when in pool, automatically and efficiently deduplicate.

pool.ts

@@ -1,5 +1,8 @@
 import {Relay, relayInit} from './relay'
 import {normalizeURL} from './utils'
+import {Filter} from './filter'
+import {Event} from './event'
+import {SubscriptionOptions, Sub} from './relay'
 
 export function pool(defaultRelays: string[] = []) {
   return new SimplePool(defaultRelays)
@@ -22,6 +25,14 @@ class SimplePool {
     const hasEventId = (id: string): boolean => this._knownIds.has(id)
     const relay = relayInit(nm, hasEventId)
     this._conn[nm] = relay
+
+    let sub = relay.sub
+    relay.sub = (filters: Filter[], opts?: SubscriptionOptions): Sub => {
+      let s = sub(filters, opts)
+      s.on('event', (event: Event) => this._knownIds.add(event.id as string))
+      return s
+    }
+
     return relay
   }
 }