fix: Don't vertically parallelize literal select (#19295)

pola-rs · Oct 18, 2024 · dae6cd9 · dae6cd9
1 parent f6b56c9
commit dae6cd9
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Showing 2 changed files with 11 additions and 3 deletions.
diff --git a/crates/polars-expr/src/expressions/alias.rs b/crates/polars-expr/src/expressions/alias.rs
@@ -59,6 +59,10 @@ impl PhysicalExpr for AliasExpr {
         ))
     }
 
+    fn is_literal(&self) -> bool {
+        self.physical_expr.is_literal()
+    }
+
     fn is_scalar(&self) -> bool {
         self.physical_expr.is_scalar()
     }

diff --git a/crates/polars-mem-engine/src/planner/lp.rs b/crates/polars-mem-engine/src/planner/lp.rs
@@ -374,16 +374,20 @@ fn create_physical_plan_impl(
                 POOL.current_num_threads() > expr.len(),
                 state.expr_depth,
             );
-
-            let streamable =
-                options.should_broadcast && all_streamable(&expr, expr_arena, Context::Default);
             let phys_expr = create_physical_expressions_from_irs(
                 &expr,
                 Context::Default,
                 expr_arena,
                 &input_schema,
                 &mut state,
             )?;
+
+            let streamable = options.should_broadcast && all_streamable(&expr, expr_arena, Context::Default)
+                // If all columns are literal we would get a 1 row per thread.
+                && !phys_expr.iter().all(|p| {
+                    p.is_literal()
+                });
+
             Ok(Box::new(executors::ProjectionExec {
                 input,
                 expr: phys_expr,