[FEAT] connect: support sample

src/daft-connect/src/translation/logical_plan.rs

@@ -6,7 +6,7 @@ use tracing::warn;
 
 use crate::translation::logical_plan::{
     aggregate::aggregate, drop::drop, filter::filter, local_relation::local_relation,
-    project::project, range::range, read::read, set_op::set_op, to_df::to_df,
+    project::project, range::range, read::read, sample::sample, set_op::set_op, to_df::to_df,
     with_columns::with_columns,
 };
 
@@ -17,6 +17,7 @@ mod local_relation;
 mod project;
 mod range;
 mod read;
+mod sample;
 mod set_op;
 mod to_df;
 mod with_columns;
@@ -87,6 +88,9 @@ pub async fn to_logical_plan(relation: Relation) -> eyre::Result<Plan> {
         RelType::SetOp(s) => set_op(*s)
             .await
             .wrap_err("Failed to apply set_op to logical plan"),
+        RelType::Sample(s) => sample(*s)
+            .await
+            .wrap_err("Failed to apply sample to logical plan"),
         plan => bail!("Unsupported relation type: {plan:?}"),
     }
 }

src/daft-connect/src/translation/logical_plan/sample.rs

@@ -0,0 +1,41 @@
+use eyre::{bail, WrapErr};
+use tracing::warn;
+
+use crate::translation::{to_logical_plan, Plan};
+
+pub async fn sample(sample: spark_connect::Sample) -> eyre::Result<Plan> {
+    let spark_connect::Sample {
+        input,
+        lower_bound,
+        upper_bound,
+        with_replacement,
+        seed,
+        deterministic_order,
+    } = sample;
+
+    let Some(input) = input else {
+        bail!("Input is required");
+    };
+
+    let mut plan = Box::pin(to_logical_plan(*input)).await?;
+
+    // Calculate fraction from bounds
+    // todo: is this correct?
+    let fraction = upper_bound - lower_bound;
+
+    let with_replacement = with_replacement.unwrap_or(false);
+
+    // we do not care about sign change
+    let seed = seed.map(|seed| seed as u64);
+
+    if deterministic_order {
+        warn!("Deterministic order is not yet supported");
+    }
+
+    plan.builder = plan
+        .builder
+        .sample(fraction, with_replacement, seed)
+        .wrap_err("Failed to apply sample to logical plan")?;
+
+    Ok(plan)
+}

tests/connect/test_sample.py

@@ -0,0 +1,18 @@
+from __future__ import annotations
+
+
+def test_sample(spark_session):
+    # Create a range DataFrame
+    df = spark_session.range(100)
+
+    # Test sample with fraction
+    sampled_df = df.sample(fraction=0.1, seed=42)
+    sampled_rows = sampled_df.collect()
+
+    # Verify sample size is roughly 10% of original
+    sample_size = len(sampled_rows)
+    assert 5 <= sample_size <= 15, f"Sample size {sample_size} should be roughly 10 rows"
+
+    # Verify sampled values are within original range
+    for row in sampled_rows:
+        assert 0 <= row["id"] < 100, f"Sampled value {row['id']} outside valid range"