expr: optimize feature flag macros WIP

src/repr/src/lib.rs

@@ -36,6 +36,7 @@ pub mod explain;
 pub mod fixed_length;
 pub mod global_id;
 pub mod namespaces;
+pub mod optimize;
 pub mod role_id;
 pub mod stats;
 pub mod strconv;

src/repr/src/optimize.rs

@@ -0,0 +1,16 @@
+// Copyright Materialize, Inc. and contributors. All rights reserved.
+//
+// Use of this software is governed by the Business Source License
+// included in the LICENSE file.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0.
+
+//! Facilities for defining optimizer feature flags.
+
+use std::collections::BTreeMap;
+
+struct OptimizerFlags {
+    vars: BTreeMap<&'static str, String>,
+}