perf(jsonrpc): add DB index to improve filter of executed outputs

- Added partial index output_executed_idx on input_epoch_application_id.
- The index contains only rows where execution_transaction_hash IS NOT NULL.
- Added the corresponding down-migration statement.

Author: renatomaia

internal/repository/postgres/schema/migrations/000001_create_initial_schema.down.sql

@@ -37,6 +37,7 @@ DROP TABLE IF EXISTS "withdrawal";
 
 DROP TRIGGER IF EXISTS "output_set_updated_at" ON "output";
 DROP INDEX IF EXISTS "output_pending_voucher_idx";
+DROP INDEX IF EXISTS "output_executed_idx";
 DROP INDEX IF EXISTS "output_raw_data_address_idx";
 DROP INDEX IF EXISTS "output_raw_data_type_idx";
 DROP TABLE IF EXISTS "output";

internal/repository/postgres/schema/migrations/000001_create_initial_schema.up.sql

@@ -450,6 +450,11 @@ WHERE "execution_transaction_hash" IS NULL AND SUBSTRING("raw_data" FROM 1 FOR 4
     E'\\x237a816f'   -- Voucher
 );
 
+-- Serves GetNumberOfExecutedOutputs without scanning the application's full
+-- output history. Outputs enter this index only after execution is observed.
+CREATE INDEX "output_executed_idx" ON "output" ("input_epoch_application_id")
+WHERE "execution_transaction_hash" IS NOT NULL;
+
 CREATE TRIGGER "output_set_updated_at" BEFORE UPDATE ON "output"
 FOR EACH ROW EXECUTE FUNCTION update_updated_at_column();