cometindex: use faster event count logging

COUNT(*) is actually relatively slow compared to taking the max rowid.
This is just for information, and spending ~1 second on this is not
worth it.

crates/util/cometindex/src/indexer.rs

@@ -141,7 +141,7 @@ impl Indexer {
         let watermark = current_watermark.unwrap_or(0);
 
         // Calculate new events count since the last watermark
-        sqlx::query_as::<_, (i64,)>("SELECT COUNT(*) FROM events WHERE rowid > $1")
+        sqlx::query_as::<_, (i64,)>("SELECT MAX(rowid) - $1 FROM events")
             .bind(watermark)
             .fetch_one(src_db)
             .await