docs: remove references to default-engine feature

CLAUDE.md

@@ -61,11 +61,10 @@ cargo +nightly fmt \
 
 ### Feature Flags
 
-- `default-engine` / `default-engine-rustls` / `default-engine-native-tls` -- async
-  Arrow/Tokio engine (pick one TLS backend)
+- `default-engine-rustls` / `default-engine-native-tls` -- async Arrow/Tokio engine (pick a TLS backend)
 - `arrow`, `arrow-XX`, `arrow-YY` -- Arrow version selection (kernel tracks the latest two
   major Arrow releases; `arrow` defaults to latest). Kernel itself does not depend on Arrow,
-  but default-engine does.
+  but the default engine does.
 - `arrow-conversion`, `arrow-expression` -- Arrow interop (auto-enabled by default engine)
 - `prettyprint` -- enables Arrow pretty-print helpers (primarily test/example oriented)
 - `clustered-table` -- clustered table write support (experimental)

README.md

@@ -55,16 +55,17 @@ consumer's own `Engine` trait, the kernel has a feature flag to enable a default
 delta_kernel = "0.21.0"
 
 # or turn on the default engine, based on latest arrow
-delta_kernel = { version = "0.21.0", features = ["default-engine", "arrow"] }
+delta_kernel = { version = "0.21.0", features = ["default-engine-rustls", "arrow"] }
 ```
 
 ### Feature flags
-There are more feature flags in addition to the `default-engine` flag shown above. Relevant flags
-include:
+There are more feature flags in addition to the `default-engine-rustls` flag shown above. Relevant
+flags include:
 
 | Feature flag  | Description   |
 | ------------- | ------------- |
-| `default-engine`    | Turn on the 'default' engine: async, arrow-based `Engine` implementation  |
+| `default-engine-rustls`    | Turn on the 'default' engine with rustls TLS backend  |
+| `default-engine-native-tls`| Turn on the 'default' engine with native-tls TLS backend  |
 | `arrow-conversion`  | Conversion utilities for arrow/kernel schema interoperation |
 | `arrow-expression`  | Expression system implementation for arrow |
 
@@ -74,8 +75,8 @@ are still unstable. We therefore may break APIs within minor releases (that is,
 we will not break APIs in patch releases (`0.1.0` -> `0.1.1`).
 
 ## Arrow versioning
-If you enable the `default-engine` feature, you get an implementation of the `Engine` trait that
-uses [Arrow] as its data format.
+If you enable a default engine feature (`default-engine-rustls` or `default-engine-native-tls`),
+you get an implementation of the `Engine` trait that uses [Arrow] as its data format.
 
 The [`arrow crate`](https://docs.rs/arrow/latest/arrow/) tends to release new major versions rather
 frequently. To enable engines that already integrate arrow to also integrate kernel and not force

ffi/cbindgen.toml

@@ -11,7 +11,6 @@ namespace = "ffi"
 cpp_compat = true
 
 [defines]
-"feature = default-engine" = "DEFINE_DEFAULT_ENGINE"
 "feature = default-engine-rustls" = "DEFINE_DEFAULT_ENGINE_RUSTLS"
 "feature = default-engine-base" = "DEFINE_DEFAULT_ENGINE_BASE"
 

kernel/Cargo.toml

@@ -117,8 +117,8 @@ arrow-expression = ["need-arrow"]
 # Schema diffing functionality (experimental)
 schema-diff = []
 
-# this is an 'internal' feature flag which has all the shared bits from default-engine and
-# default-engine-rustls
+# this is an 'internal' feature flag which has all the shared bits from default-engine-native-tls
+# and default-engine-rustls
 default-engine-base = [
   "arrow-conversion",
   "arrow-expression",

kernel/src/engine/mod.rs

@@ -1,6 +1,6 @@
 //! Provides an engine implementation that implements the required traits. The engine can optionally
-//! be built into the kernel by setting the `default-engine` feature flag. See the related module
-//! for more information.
+//! be built into the kernel by setting the `default-engine-rustls` or `default-engine-native-tls`
+//! feature flag. See the related module for more information.
 
 #[cfg(feature = "arrow-expression")]
 use crate::parquet::arrow::arrow_reader::ArrowReaderOptions;