feat(cold-sql): add topic indexes for log filtering

crates/cold-sql/migrations/002_add_topic_indexes.sql

@@ -0,0 +1,9 @@
+-- Add indexes on topic1, topic2, topic3 for log filtering.
+--
+-- topic0 already has an index (001_initial). Most ERC-20/721
+-- Transfer lookups filter on topic1 (from) or topic2 (to), which
+-- previously required sequential scans.
+
+CREATE INDEX IF NOT EXISTS idx_logs_topic1 ON logs (topic1);
+CREATE INDEX IF NOT EXISTS idx_logs_topic2 ON logs (topic2);
+CREATE INDEX IF NOT EXISTS idx_logs_topic3 ON logs (topic3);

crates/cold-sql/src/backend.rs

@@ -128,6 +128,9 @@ impl SqlColdBackend {
         // connection that subsequent queries will use.
         let is_postgres = backend == "PostgreSQL";
         sqlx::raw_sql(migration).execute(&pool).await?;
+        sqlx::raw_sql(include_str!("../migrations/002_add_topic_indexes.sql"))
+            .execute(&pool)
+            .await?;
         Ok(Self { pool, is_postgres })
     }