perf(udf): pointer-identity fast path in PartialEq for Python UDFs

`PartialEq` was acquiring the GIL on every comparison via
`Python::attach`, just to call `__eq__` on the stored callable. Most
equality checks compare `Arc`-shared clones of the same UDF
(expression rewriting, plan diffing), where pointer identity already
settles the question — no Python call needed.

Add `Py::as_ptr` pointer comparison before the `Python::attach` branch
on all three impls (scalar / aggregate / window). Falls through to the
GIL-bound `__eq__` only when the two callables are distinct objects.

No behavior change for unequal-pointer cases; the equal-pointer case
now skips the GIL roundtrip entirely.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: timsaucer

crates/core/src/udaf.rs

@@ -238,12 +238,16 @@ impl PartialEq for PythonFunctionAggregateUDF {
             && self.signature == other.signature
             && self.return_type == other.return_type
             && self.state_fields == other.state_fields
-            && Python::attach(|py| {
-                self.accumulator
-                    .bind(py)
-                    .eq(other.accumulator.bind(py))
-                    .unwrap_or(false)
-            })
+            // Pointer-identity fast path: `Arc`-shared clones of the
+            // same UDF skip the GIL roundtrip. Falls through to Python
+            // `__eq__` only for two distinct callables.
+            && (self.accumulator.as_ptr() == other.accumulator.as_ptr()
+                || Python::attach(|py| {
+                    self.accumulator
+                        .bind(py)
+                        .eq(other.accumulator.bind(py))
+                        .unwrap_or(false)
+                }))
     }
 }
 

crates/core/src/udf.rs

@@ -106,7 +106,14 @@ impl PartialEq for PythonFunctionScalarUDF {
         self.name == other.name
             && self.signature == other.signature
             && self.return_field == other.return_field
-            && Python::attach(|py| self.func.bind(py).eq(other.func.bind(py)).unwrap_or(false))
+            // Identical pointers ⇒ same Python object. Most equality
+            // checks compare `Arc`-shared clones of the same UDF
+            // (e.g. expression rewriting), so the pointer match short-
+            // circuits before touching the GIL.
+            && (self.func.as_ptr() == other.func.as_ptr()
+                || Python::attach(|py| {
+                    self.func.bind(py).eq(other.func.bind(py)).unwrap_or(false)
+                }))
     }
 }
 

crates/core/src/udwf.rs

@@ -319,12 +319,16 @@ impl PartialEq for PythonFunctionWindowUDF {
         self.name == other.name
             && self.signature == other.signature
             && self.return_type == other.return_type
-            && Python::attach(|py| {
-                self.evaluator
-                    .bind(py)
-                    .eq(other.evaluator.bind(py))
-                    .unwrap_or(false)
-            })
+            // Pointer-identity fast path: `Arc`-shared clones of the
+            // same UDF skip the GIL roundtrip. Falls through to Python
+            // `__eq__` only for two distinct callables.
+            && (self.evaluator.as_ptr() == other.evaluator.as_ptr()
+                || Python::attach(|py| {
+                    self.evaluator
+                        .bind(py)
+                        .eq(other.evaluator.bind(py))
+                        .unwrap_or(false)
+                }))
     }
 }