Remove DeltaScheme from default BtrBlocksCompressor (#9967)

This should be included once we add filtering

Signed-off-by: Robert Kruszewski <github@robertk.io>

Author: robert3005

vortex-btrblocks/src/builder.rs

@@ -36,8 +36,7 @@ pub const ALL_SCHEMES: &[&dyn Scheme] = &[
     &integer::RunEndScheme,
     &integer::SequenceScheme,
     &integer::IntRLEScheme,
-    // Prefer all other schemes above delta, for now (since its slower to decompress).
-    &integer::DeltaScheme::new(1.25),
+    // Delta is omitted here: see [`DELTA_SCHEME`].
     ////////////////////////////////////////////////////////////////////////////////////////////////
     // Float schemes.
     ////////////////////////////////////////////////////////////////////////////////////////////////
@@ -66,6 +65,13 @@ pub const ALL_SCHEMES: &[&dyn Scheme] = &[
     &temporal::TemporalScheme,
 ];
 
+/// Delta, kept out of [`ALL_SCHEMES`] because it is slower to decompress than the schemes that
+/// would otherwise win. Callers that want it opt in with
+/// [`with_new_scheme`](BtrBlocksCompressorBuilder::with_new_scheme).
+///
+/// TODO(robert): Return it to [`ALL_SCHEMES`] once we have scheme filtering.
+pub static DELTA_SCHEME: integer::DeltaScheme = integer::DeltaScheme::new(1.25);
+
 /// Builder for creating configured [`BtrBlocksCompressor`] instances.
 ///
 /// By default, all schemes in [`ALL_SCHEMES`] are enabled in a deterministic order. Feature-gated

vortex-btrblocks/src/lib.rs

@@ -78,6 +78,7 @@ mod trace_tests;
 // Btrblocks-specific exports.
 pub use builder::ALL_SCHEMES;
 pub use builder::BtrBlocksCompressorBuilder;
+pub use builder::DELTA_SCHEME;
 pub use canonical_compressor::BtrBlocksCompressor;
 pub use schemes::patches::compress_patches;
 pub use vortex_compressor::CascadingCompressor;

vortex-btrblocks/src/schemes/integer/scheme_selection_tests.rs

@@ -28,6 +28,8 @@ use vortex_session::VortexSession;
 use vortex_sparse::Sparse;
 
 use crate::BtrBlocksCompressor;
+use crate::BtrBlocksCompressorBuilder;
+use crate::DELTA_SCHEME;
 static SESSION: LazyLock<VortexSession> = LazyLock::new(vortex_array::array_session);
 
 #[test]
@@ -174,7 +176,9 @@ fn test_delta_compressed() -> VortexResult<()> {
         .collect();
     let array = PrimitiveArray::new(Buffer::copy_from(&values), Validity::NonNullable);
 
-    let btr = BtrBlocksCompressor::default();
+    let btr = BtrBlocksCompressorBuilder::default()
+        .with_new_scheme(&DELTA_SCHEME)
+        .build();
     let compressed = btr.compress(
         &array.clone().into_array(),
         &mut SESSION.create_execution_ctx(),
@@ -212,7 +216,9 @@ fn test_delta_compressed_unaligned_length() -> VortexResult<()> {
         .collect();
     let array = PrimitiveArray::new(Buffer::copy_from(&values), Validity::NonNullable);
 
-    let btr = BtrBlocksCompressor::default();
+    let btr = BtrBlocksCompressorBuilder::default()
+        .with_new_scheme(&DELTA_SCHEME)
+        .build();
     let compressed = btr.compress(
         &array.clone().into_array(),
         &mut SESSION.create_execution_ctx(),
@@ -239,7 +245,9 @@ fn test_delta_nullable_unaligned_sum() -> VortexResult<()> {
     let array =
         PrimitiveArray::from_option_iter(iter::once(None).chain((1i32..=100_000).map(Some)));
 
-    let btr = BtrBlocksCompressor::default();
+    let btr = BtrBlocksCompressorBuilder::default()
+        .with_new_scheme(&DELTA_SCHEME)
+        .build();
     let compressed = btr.compress(&array.clone().into_array(), &mut ctx)?;
     assert!(
         compressed.is::<Delta>(),

vortex-btrblocks/src/trace_tests.rs

@@ -53,7 +53,8 @@ use vortex_error::VortexResult;
 use vortex_mask::Mask;
 use vortex_session::VortexSession;
 
-use crate::BtrBlocksCompressor;
+use crate::BtrBlocksCompressorBuilder;
+use crate::DELTA_SCHEME;
 
 /// A session with the default Vortex encodings registered.
 ///
@@ -124,8 +125,12 @@ fn lineitem() -> VortexResult<ArrayRef> {
         .from_arrow_record_batch(batch, &schema)
 }
 
+/// Delta is opt-in, and these traces cover the delta-encoded FSST offsets, so enable it here.
 fn compressed_lineitem() -> VortexResult<ArrayRef> {
-    BtrBlocksCompressor::default().compress(&lineitem()?, &mut execution_ctx())
+    BtrBlocksCompressorBuilder::default()
+        .with_new_scheme(&DELTA_SCHEME)
+        .build()
+        .compress(&lineitem()?, &mut execution_ctx())
 }
 
 fn field(array: &ArrayRef, name: &str) -> VortexResult<ArrayRef> {