perf: cache apply_parameters to avoid repeated type() class creation

Cache the results of _CassandraType.apply_parameters() in a class-level
dict keyed by (cls, subtypes, names). This avoids the expensive type()
metaclass machinery on repeated calls with the same type signature,
which is the common case during result-set deserialization.

Benchmark: 31.7x speedup (6.48 us/call -> 0.20 us/call) for cached hits.

Author: mykaul

benchmarks/bench_cache_apply_parameters.py

@@ -0,0 +1,78 @@
+# Copyright DataStax, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Micro-benchmark: apply_parameters caching.
+
+Measures the speedup from caching parameterized type creation
+in _CassandraType.apply_parameters().
+
+Run:
+    python benchmarks/bench_cache_apply_parameters.py
+"""
+import timeit
+from cassandra.cqltypes import (
+    MapType, SetType, ListType, TupleType,
+    Int32Type, UTF8Type, FloatType, DoubleType, BooleanType,
+    _CassandraType,
+)
+
+
+def bench_apply_parameters():
+    """Benchmark apply_parameters with cache (repeated calls)."""
+    cache = _CassandraType._apply_parameters_cache
+
+    # Warm up the cache
+    MapType.apply_parameters([UTF8Type, Int32Type])
+    SetType.apply_parameters([FloatType])
+    ListType.apply_parameters([DoubleType])
+    TupleType.apply_parameters([Int32Type, UTF8Type, BooleanType])
+
+    calls = [
+        (MapType, [UTF8Type, Int32Type]),
+        (SetType, [FloatType]),
+        (ListType, [DoubleType]),
+        (TupleType, [Int32Type, UTF8Type, BooleanType]),
+    ]
+
+    def run_cached():
+        for cls, subtypes in calls:
+            cls.apply_parameters(subtypes)
+
+    # Benchmark cached path
+    n = 100_000
+    t_cached = timeit.timeit(run_cached, number=n)
+    print(f"Cached apply_parameters ({len(calls)} types x {n} iters): "
+          f"{t_cached:.3f}s  ({t_cached / (n * len(calls)) * 1e6:.2f} us/call)")
+
+    # Benchmark uncached path (clear cache each iteration)
+    def run_uncached():
+        for cls, subtypes in calls:
+            cache.clear()
+            cls.apply_parameters(subtypes)
+
+    t_uncached = timeit.timeit(run_uncached, number=n)
+    print(f"Uncached apply_parameters ({len(calls)} types x {n} iters): "
+          f"{t_uncached:.3f}s  ({t_uncached / (n * len(calls)) * 1e6:.2f} us/call)")
+
+    speedup = t_uncached / t_cached
+    print(f"Speedup: {speedup:.1f}x")
+
+
+def main():
+    bench_apply_parameters()
+
+
+if __name__ == '__main__':
+    main()

cassandra/cqltypes.py

@@ -275,6 +275,7 @@ class _CassandraType(object, metaclass=CassandraTypeType):
     subtypes = ()
     num_subtypes = 0
     empty_binary_ok = False
+    _apply_parameters_cache = {}
 
     support_empty_values = False
     """
@@ -373,8 +374,15 @@ def apply_parameters(cls, subtypes, names=None):
         if cls.num_subtypes != 'UNKNOWN' and len(subtypes) != cls.num_subtypes:
             raise ValueError("%s types require %d subtypes (%d given)"
                              % (cls.typename, cls.num_subtypes, len(subtypes)))
+        subtypes = tuple(subtypes)
+        cache_key = (cls, subtypes, tuple(names) if names else names)
+        cached = cls._apply_parameters_cache.get(cache_key)
+        if cached is not None:
+            return cached
         newname = cls.cass_parameterized_type_with(subtypes)
-        return type(newname, (cls,), {'subtypes': subtypes, 'cassname': cls.cassname, 'fieldnames': names})
+        result = type(newname, (cls,), {'subtypes': subtypes, 'cassname': cls.cassname, 'fieldnames': names})
+        cls._apply_parameters_cache[cache_key] = result
+        return result
 
     @classmethod
     def cql_parameterized_type(cls):

tests/unit/test_cache_apply_parameters.py

@@ -0,0 +1,90 @@
+"""
+Unit tests for apply_parameters caching in _CassandraType.
+"""
+import unittest
+from cassandra.cqltypes import (
+    MapType, SetType, ListType, TupleType,
+    Int32Type, UTF8Type, FloatType, DoubleType, BooleanType,
+    _CassandraType,
+)
+
+
+class TestApplyParametersCache(unittest.TestCase):
+
+    def setUp(self):
+        _CassandraType._apply_parameters_cache.clear()
+
+    def test_cache_returns_same_object(self):
+        """Repeated apply_parameters calls return the exact same class object."""
+        result1 = MapType.apply_parameters([UTF8Type, Int32Type])
+        result2 = MapType.apply_parameters([UTF8Type, Int32Type])
+        self.assertIs(result1, result2)
+
+    def test_cache_different_subtypes_different_results(self):
+        """Different subtype combinations produce different cached classes."""
+        r1 = MapType.apply_parameters([UTF8Type, Int32Type])
+        r2 = MapType.apply_parameters([Int32Type, UTF8Type])
+        self.assertIsNot(r1, r2)
+
+    def test_cache_different_base_types(self):
+        """Different base types with same subtypes produce different classes."""
+        r1 = SetType.apply_parameters([Int32Type])
+        r2 = ListType.apply_parameters([Int32Type])
+        self.assertIsNot(r1, r2)
+
+    def test_cached_type_has_correct_subtypes(self):
+        """Cached types preserve their subtype information."""
+        result = MapType.apply_parameters([UTF8Type, FloatType])
+        self.assertEqual(result.subtypes, (UTF8Type, FloatType))
+        # Call again, verify cache hit still has correct subtypes
+        result2 = MapType.apply_parameters([UTF8Type, FloatType])
+        self.assertEqual(result2.subtypes, (UTF8Type, FloatType))
+
+    def test_cached_type_has_correct_cassname(self):
+        """Cached types preserve their cassname."""
+        result = SetType.apply_parameters([DoubleType])
+        self.assertEqual(result.cassname, SetType.cassname)
+
+    def test_cached_type_with_names(self):
+        """Caching works correctly with named parameters (UDT-style)."""
+        r1 = TupleType.apply_parameters([Int32Type, UTF8Type], names=['id', 'name'])
+        r2 = TupleType.apply_parameters([Int32Type, UTF8Type], names=['id', 'name'])
+        self.assertIs(r1, r2)
+
+    def test_different_names_different_cache_entries(self):
+        """Different names produce different cached classes."""
+        r1 = TupleType.apply_parameters([Int32Type, UTF8Type], names=['id', 'name'])
+        r2 = TupleType.apply_parameters([Int32Type, UTF8Type], names=['key', 'value'])
+        self.assertIsNot(r1, r2)
+
+    def test_names_none_vs_no_names(self):
+        """Passing names=None and not passing names use the same cache entry."""
+        r1 = MapType.apply_parameters([UTF8Type, Int32Type], names=None)
+        r2 = MapType.apply_parameters([UTF8Type, Int32Type])
+        self.assertIs(r1, r2)
+
+    def test_tuple_subtypes_accepted(self):
+        """Both list and tuple subtypes produce the same cached result."""
+        r1 = MapType.apply_parameters([UTF8Type, Int32Type])
+        r2 = MapType.apply_parameters((UTF8Type, Int32Type))
+        self.assertIs(r1, r2)
+
+    def test_cache_populated(self):
+        """The cache dict is populated after apply_parameters calls."""
+        _CassandraType._apply_parameters_cache.clear()
+        MapType.apply_parameters([UTF8Type, Int32Type])
+        self.assertGreater(len(_CassandraType._apply_parameters_cache), 0)
+
+    def test_cache_clear_forces_new_creation(self):
+        """Clearing the cache forces new type creation."""
+        r1 = MapType.apply_parameters([UTF8Type, Int32Type])
+        _CassandraType._apply_parameters_cache.clear()
+        r2 = MapType.apply_parameters([UTF8Type, Int32Type])
+        # After clearing, we get a new class (different object identity)
+        self.assertIsNot(r1, r2)
+        # But they should be functionally equivalent
+        self.assertEqual(r1.subtypes, r2.subtypes)
+
+
+if __name__ == '__main__':
+    unittest.main()