feat[expr]: N-ary CASE WHEN expression

vortex-array/Cargo.toml

@@ -129,6 +129,11 @@ name = "expr_large_struct_pack"
 path = "benches/expr/large_struct_pack.rs"
 harness = false
 
+[[bench]]
+name = "expr_case_when"
+path = "benches/expr/case_when_bench.rs"
+harness = false
+
 [[bench]]
 name = "chunked_dict_builder"
 harness = false

vortex-array/benches/expr/case_when_bench.rs

@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright the Vortex contributors
+
+#![allow(clippy::unwrap_used)]
+#![allow(clippy::cast_possible_truncation)]
+
+use std::sync::LazyLock;
+
+use divan::Bencher;
+use vortex_array::ArrayRef;
+use vortex_array::Canonical;
+use vortex_array::IntoArray;
+use vortex_array::VortexSessionExecute;
+use vortex_array::arrays::StructArray;
+use vortex_array::expr::case_when;
+use vortex_array::expr::get_item;
+use vortex_array::expr::gt;
+use vortex_array::expr::lit;
+use vortex_array::expr::root;
+use vortex_array::session::ArraySession;
+use vortex_array::validity::Validity;
+use vortex_buffer::Buffer;
+use vortex_dtype::FieldNames;
+use vortex_session::VortexSession;
+
+static SESSION: LazyLock<VortexSession> =
+    LazyLock::new(|| VortexSession::empty().with::<ArraySession>());
+
+fn main() {
+    divan::main();
+}
+
+fn make_struct_array(size: usize) -> ArrayRef {
+    let data: Buffer<i32> = (0..size as i32).collect();
+    let field = data.into_array();
+    StructArray::try_new(
+        FieldNames::from(["value"]),
+        vec![field],
+        size,
+        Validity::NonNullable,
+    )
+    .unwrap()
+    .into_array()
+}
+
+/// Benchmark a simple binary CASE WHEN with varying array sizes.
+#[divan::bench(args = [1000, 10000, 100000])]
+fn case_when_simple(bencher: Bencher, size: usize) {
+    let array = make_struct_array(size);
+
+    // CASE WHEN value > 500 THEN 100 ELSE 0 END
+    let expr = case_when([
+        gt(get_item("value", root()), lit(500i32)),
+        lit(100i32),
+        lit(0i32),
+    ]);
+
+    bencher
+        .with_inputs(|| (&expr, &array, SESSION.create_execution_ctx()))
+        .bench_refs(|(expr, array, ctx)| {
+            array
+                .apply(expr)
+                .unwrap()
+                .execute::<Canonical>(ctx)
+                .unwrap()
+        });
+}
+
+/// Benchmark n-ary CASE WHEN with multiple conditions.
+#[divan::bench(args = [1000, 10000, 100000])]
+fn case_when_nary_3_conditions(bencher: Bencher, size: usize) {
+    let array = make_struct_array(size);
+
+    // CASE WHEN value > 750 THEN 3 WHEN value > 500 THEN 2 WHEN value > 250 THEN 1 ELSE 0 END
+    let expr = case_when([
+        gt(get_item("value", root()), lit(750i32)),
+        lit(3i32),
+        gt(get_item("value", root()), lit(500i32)),
+        lit(2i32),
+        gt(get_item("value", root()), lit(250i32)),
+        lit(1i32),
+        lit(0i32),
+    ]);
+
+    bencher
+        .with_inputs(|| (&expr, &array, SESSION.create_execution_ctx()))
+        .bench_refs(|(expr, array, ctx)| {
+            array
+                .apply(expr)
+                .unwrap()
+                .execute::<Canonical>(ctx)
+                .unwrap()
+        });
+}
+
+/// Benchmark CASE WHEN where all conditions are true (short-circuit path).
+#[divan::bench(args = [1000, 10000, 100000])]
+fn case_when_all_true(bencher: Bencher, size: usize) {
+    let array = make_struct_array(size);
+
+    // CASE WHEN value >= 0 THEN 100 ELSE 0 END (always true for our data)
+    let expr = case_when([
+        gt(get_item("value", root()), lit(-1i32)),
+        lit(100i32),
+        lit(0i32),
+    ]);
+
+    bencher
+        .with_inputs(|| (&expr, &array, SESSION.create_execution_ctx()))
+        .bench_refs(|(expr, array, ctx)| {
+            array
+                .apply(expr)
+                .unwrap()
+                .execute::<Canonical>(ctx)
+                .unwrap()
+        });
+}
+
+/// Benchmark CASE WHEN where all conditions are false (short-circuit path).
+#[divan::bench(args = [1000, 10000, 100000])]
+fn case_when_all_false(bencher: Bencher, size: usize) {
+    let array = make_struct_array(size);
+
+    // CASE WHEN value > 1000000 THEN 100 ELSE 0 END (always false for our data)
+    let expr = case_when([
+        gt(get_item("value", root()), lit(1_000_000i32)),
+        lit(100i32),
+        lit(0i32),
+    ]);
+
+    bencher
+        .with_inputs(|| (&expr, &array, SESSION.create_execution_ctx()))
+        .bench_refs(|(expr, array, ctx)| {
+            array
+                .apply(expr)
+                .unwrap()
+                .execute::<Canonical>(ctx)
+                .unwrap()
+        });
+}
+
+/// Benchmark n-ary CASE WHEN with 10 conditions.
+#[divan::bench(args = [1000, 10000, 100000])]
+fn case_when_nary_10_conditions(bencher: Bencher, size: usize) {
+    let array = make_struct_array(size);
+
+    // Build 10 WHEN/THEN pairs with decreasing thresholds
+    let expr = case_when([
+        gt(get_item("value", root()), lit(900i32)),
+        lit(10i32),
+        gt(get_item("value", root()), lit(800i32)),
+        lit(9i32),
+        gt(get_item("value", root()), lit(700i32)),
+        lit(8i32),
+        gt(get_item("value", root()), lit(600i32)),
+        lit(7i32),
+        gt(get_item("value", root()), lit(500i32)),
+        lit(6i32),
+        gt(get_item("value", root()), lit(400i32)),
+        lit(5i32),
+        gt(get_item("value", root()), lit(300i32)),
+        lit(4i32),
+        gt(get_item("value", root()), lit(200i32)),
+        lit(3i32),
+        gt(get_item("value", root()), lit(100i32)),
+        lit(2i32),
+        gt(get_item("value", root()), lit(0i32)),
+        lit(1i32),
+        lit(0i32), // else
+    ]);
+
+    bencher
+        .with_inputs(|| (&expr, &array, SESSION.create_execution_ctx()))
+        .bench_refs(|(expr, array, ctx)| {
+            array
+                .apply(expr)
+                .unwrap()
+                .execute::<Canonical>(ctx)
+                .unwrap()
+        });
+}
+
+/// Benchmark n-ary CASE WHEN with 100 conditions.
+#[divan::bench(args = [1000, 10000, 100000])]
+fn case_when_nary_100_conditions(bencher: Bencher, size: usize) {
+    use vortex_array::expr::Expression;
+
+    let array = make_struct_array(size);
+
+    // Build 100 WHEN/THEN pairs programmatically
+    let mut children: Vec<Expression> = Vec::with_capacity(201);
+    for i in (1..=100).rev() {
+        let threshold = i * 10; // thresholds: 1000, 990, 980, ..., 10
+        children.push(gt(get_item("value", root()), lit(threshold)));
+        children.push(lit(i));
+    }
+    children.push(lit(0i32)); // else
+
+    let expr = case_when(children);
+
+    bencher
+        .with_inputs(|| (&expr, &array, SESSION.create_execution_ctx()))
+        .bench_refs(|(expr, array, ctx)| {
+            array
+                .apply(expr)
+                .unwrap()
+                .execute::<Canonical>(ctx)
+                .unwrap()
+        });
+}