bench: write Lance at storage version 2.2 in the compression benchmark

benchmarks/compress-bench/README.md

@@ -23,6 +23,20 @@ See [`src/main.rs`](./src/main.rs) for the dataset list and CLI flags (`--format
 cargo run -p compress-bench --profile release_debug
 ```
 
+Lance is behind the `lance` feature, and `--formats` accepts it only in a binary built with
+it. Only the post-merge `develop` benchmark covers Lance; the pull-request `Compression`
+comment does not, to keep the PR matrix cheap:
+
+```bash
+cargo run -p compress-bench --profile release_debug --features lance \
+  -- --formats arrow-ipc,parquet,lance,vortex
+```
+
+Lance files are written at storage version 2.2, the newest stable version. Storage versions at or
+above 2.1 use structural encoding, which is what applies Lance's compressive encodings — bitpacking,
+FSST, general compression. Note that `LanceFileVersion::Stable` resolves to 2.1, the default for new
+datasets, rather than to the newest stable version, so 2.2 has to be named explicitly.
+
 ## GPU decompression
 
 `--gpu-decompress` is opt-in, requires the `cuda` feature, and restricts the suite to the

benchmarks/lance-bench/src/compress.rs

@@ -148,7 +148,10 @@ impl Compressor for LanceCompressor {
             .to_str()
             .ok_or_else(|| anyhow!("Failed to convert path to str"))?;
         let reader_iter = RecordBatchIterator::new(batches.into_iter().map(Ok), Arc::clone(schema));
-        let write_params = WriteParams::with_storage_version(LanceFileVersion::V2_0);
+        // Storage versions at or above 2.1 use structural encoding, which is what applies
+        // Lance's compressive encodings. Not `Stable`: that resolves to the default version for
+        // new datasets, 2.1, rather than to the newest stable one, which is 2.2.
+        let write_params = WriteParams::with_storage_version(LanceFileVersion::V2_2);
         Dataset::write(reader_iter, path_str, Some(write_params)).await?;
 
         let elapsed = start.elapsed();

scripts/compress-split.py

@@ -84,7 +84,8 @@ def main() -> None:
     parser.add_argument(
         "--formats",
         default="arrow-ipc,parquet,vortex",
-        help="comma-separated formats to forward to compress-bench",
+        help="comma-separated formats to forward to compress-bench "
+        "(lance requires a binary built with --features lance)",
     )
     parser.add_argument(
         "--emit-ingest-records",