fix(coprocessor): add missing indices for ciphertext_digest table (#1…

coprocessor/fhevm-engine/db-migration/migrations/20251203140023_ciphertext_digest_idx_sent_and_handle.sql

@@ -0,0 +1,11 @@
+-- Track when entries are created for fair queuing of unsent transactions.
+ALTER TABLE ciphertext_digest
+ADD COLUMN IF NOT EXISTS created_at TIMESTAMP NOT NULL DEFAULT NOW();
+
+-- Handle SELECTs on handle only by the txn-sender.
+CREATE INDEX IF NOT EXISTS idx_ciphertext_digest_handle
+ON ciphertext_digest (handle);
+
+-- Handle SELECTs on unsent txns with limited retries by the txn-sender.
+CREATE INDEX IF NOT EXISTS idx_ciphertext_digest_unsent
+ON ciphertext_digest (txn_is_sent, created_at);

coprocessor/fhevm-engine/transaction-sender/src/ops/add_ciphertext.rs

@@ -310,6 +310,7 @@ where
             AND ciphertext IS NOT NULL
             AND ciphertext128 IS NOT NULL
             AND txn_limited_retries_count < $1
+            ORDER BY created_at ASC
             LIMIT $2",
             self.conf.add_ciphertexts_max_retries,
             self.conf.add_ciphertexts_batch_limit as i64,