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fix: Prevent predicate pushdown across Sort with baked-in slice #26804

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Merged
ritchie46 merged 2 commits into from
Mar 5, 2026
Merged

fix: Prevent predicate pushdown across Sort with baked-in slice #26804

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4a7cfc3
don't push predicates past Sort with baked-in slice
gautamvarmadatla Mar 4, 2026
ab37e5c
minor
ritchie46 Mar 5, 2026
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17 changes: 10 additions & 7 deletions crates/polars-plan/src/plans/optimizer/predicate_pushdown/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -196,12 +196,7 @@ impl PredicatePushDown {
let new_inputs = inputs
.map(|node| {
let alp = lp_arena.take(node);
let alp = self.push_down(
alp,
init_hashmap(Some(acc_predicates.len())),
lp_arena,
expr_arena,
)?;
let alp = self.push_down(alp, init_hashmap(None), lp_arena, expr_arena)?;
lp_arena.replace(node, alp);
Ok(node)
})
Expand Down Expand Up @@ -581,6 +576,12 @@ impl PredicatePushDown {
mut slice,
sort_options,
} => {
let mut local_predicates = Vec::new();
if slice.is_some() && !acc_predicates.is_empty() {
local_predicates = acc_predicates.into_values().collect();
acc_predicates = init_hashmap(None);
}

if let Some((offset, len, None)) = slice
&& by_column.len() == 1
{
Expand All @@ -600,7 +601,9 @@ impl PredicatePushDown {
slice,
sort_options,
};
self.pushdown_and_continue(lp, acc_predicates, lp_arena, expr_arena, true)
let lp =
self.pushdown_and_continue(lp, acc_predicates, lp_arena, expr_arena, true)?;
Ok(self.optional_apply_predicate(lp, local_predicates, lp_arena, expr_arena))
},
lp @ Sink { .. } | lp @ SinkMultiple { .. } => {
self.pushdown_and_continue(lp, acc_predicates, lp_arena, expr_arena, false)
Expand Down
28 changes: 28 additions & 0 deletions py-polars/tests/unit/lazyframe/test_predicates.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1293,3 +1293,31 @@ def test_projection_pushed_past_join_26693() -> None:
plan = a.filter(pl.col.y > 0).join(b, on="x").group_by("x").agg([]).explain()

assert plan.index("simple π") > plan.index("INNER JOIN")


def test_predicate_pushdown_sort_slice_26803() -> None:
df = pl.DataFrame({"rank": [1, 2, 3, 4, 5], "score": [10, 4, 6, 2, 8]})

for lazy, eager in [
(
df.lazy().sort("rank").head(3).filter(pl.col("rank") > 2),
df.sort("rank").head(3).filter(pl.col("rank") > 2),
),
(
df.lazy().sort("rank").tail(3).filter(pl.col("rank") < 4),
df.sort("rank").tail(3).filter(pl.col("rank") < 4),
),
(
df.lazy().sort("rank", descending=True).head(3).filter(pl.col("rank") < 4),
df.sort("rank", descending=True).head(3).filter(pl.col("rank") < 4),
),
(
df.lazy().top_k(3, by="rank").filter(pl.col("rank") < 5),
df.top_k(3, by="rank").filter(pl.col("rank") < 5),
),
(
df.lazy().bottom_k(3, by="rank").filter(pl.col("rank") > 1),
df.bottom_k(3, by="rank").filter(pl.col("rank") > 1),
),
]:
assert_frame_equal(lazy.collect(), eager, check_row_order=False)
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