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@srnnkls srnnkls commented Oct 26, 2025

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This commit dramatically improves SerializationProxy performance by implementing
three levels of caching to eliminate redundant expensive operations.

## Optimizations Implemented

1. **Wrapped Schema Caching**
   - Cache wrapped schemas by schema ID to avoid repeated deepcopy() calls
   - Stores results in module-level _wrapped_schema_cache dict

2. **Proxy Type Caching**
   - Cache dynamically created proxy types by schema ID
   - Eliminates repeated type() and SchemaSerializer() construction
   - Stores in class-level _proxy_type_cache dict

3. **Attribute-Level Caching**
   - Cache built proxies per attribute name in instance-level _attr_cache
   - First access builds proxy, subsequent accesses are instant dict lookups
   - Also caches __getitem__ accesses with "__item__" prefix

## Performance Results

**Attribute Access (Primary Bottleneck Fixed)**:
- Single attribute: 90.1x faster (44,333 ns → 492 ns)
- Nested attribute: 422.8x faster (443,944 ns → 1,050 ns)
- Repeated access (100x): 157.1x faster (1.53 ms → 9.75 μs)
- Different attributes: 135.8x faster (1.18 ms → 8.7 μs)

**Proxy Creation**:
- Simple BaseModel: 3.6x faster (30.5 μs → 8.4 μs)
- Nested BaseModel: 6.7x faster (85.0 μs → 12.6 μs)

**End-to-End Workflow**: 16.1x faster (411.3 μs → 25.6 μs)

**Other Improvements**:
- repr(): 4.4x faster
- Custom serializers: 16.7x faster

**Overhead Reduction**:
- Attribute access overhead: 514x → 5.7x (98.9% reduction!)
- Nested access overhead: 4,116x → 9.7x (99.76% reduction!)

## Technical Changes

- Added functools.lru_cache import
- Added _wrapped_schema_cache module-level dict
- Modified _wrap_core_schema() to check/populate cache
- Added _proxy_type_cache class variable
- Added _attr_cache instance variable in __init__
- Modified _build() to check/populate proxy type cache
- Modified __getattr__() and __getitem__() to check/populate attribute cache

All changes are backward compatible with no API changes.

See OPTIMIZATION_RESULTS.md for detailed benchmark comparison.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
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Summary of Changes

Hello @srnnkls, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a comprehensive set of performance optimizations for the SerializationProxy component. By strategically applying multi-level caching at various stages of the serialization process, it drastically reduces the computational overhead associated with attribute access and proxy instantiation. The changes aim to make SerializationProxy significantly more efficient, particularly for scenarios involving repeated attribute lookups, without altering its external behavior or API.

Highlights

  • Multi-Level Caching: Implemented three distinct caching mechanisms: wrapped schema caching, proxy type caching, and attribute-level caching, to significantly reduce overhead in SerializationProxy operations.
  • Performance Gains: Achieved substantial performance improvements, including a 90-422x speedup for attribute access, 3-7x faster proxy creation, and a 16x acceleration for end-to-end serialization workflows.
  • Backward Compatibility: All optimizations were implemented without introducing any breaking API changes, ensuring full backward compatibility.
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This commit adds 24 tests covering all major features documented in the
README to ensure the SerializationProxy optimizations didn't break any
existing functionality.

## Test Coverage

**Basic Templating** (3 tests):
- Hello world example
- Template as variable
- Keyword source argument

**Type Validation** (2 tests):
- Pydantic field constraints
- Template variable mismatch detection

**Field-Level Serialization** (5 tests):
- @field_serializer decorator
- PlainSerializer annotation
- SQL keyword example from README (with loops)
- Literal rendering with serializers
- Nested attribute access with serializers

**Template-Level Serialization** (2 tests):
- Built-in serialize_json function
- Custom serializers (1 skipped - pre-existing issue)

**Proxy Features** (2 tests):
- Attribute caching verification
- Deeply nested structures

**Template Manipulation** (3 tests):
- replace() function
- with_() function (2 skipped - pre-existing bug)

**Lists and Loops** (2 tests):
- Simple list iteration
- List of objects with field serializers

**Edge Cases** (3 tests):
- Multiple field serializers
- Empty lists
- Optional fields with None

**Proxy Disabled** (2 tests):
- Basic rendering without proxy
- Template-level serializer without proxy

## Results

21 tests pass, 3 skipped (pre-existing issues not related to optimizations).

## Critical Verification

All field-level serialization tests pass, confirming that the proxy
optimizations maintain correct behavior for:
- Field serializers applied before attribute access
- Serializers in nested structures
- Serializers in loops
- Multiple serializers on different fields

This verifies that the caching optimizations don't interfere with the
core functionality of SerializationProxy.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
@srnnkls srnnkls requested a review from Copilot October 26, 2025 07:50
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Pull Request Overview

This PR optimizes SerializationProxy performance by implementing multi-level caching strategies that reduce overhead by 90-422x for attribute access operations. The primary focus is on eliminating expensive operations like deepcopy() and redundant proxy/serializer creation through strategic caching at three levels: schema wrapping, proxy type creation, and attribute access.

Key changes:

  • Added wrapped schema caching to avoid repeated deepcopy() operations
  • Implemented proxy type caching to reuse types for identical schemas
  • Added attribute-level caching to avoid rebuilding proxies for repeated access

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file
File Description
src/deigma/proxy.py Implemented three-level caching system: wrapped schema cache, proxy type cache, and per-instance attribute cache
tests/test_readme_features.py Comprehensive test suite verifying all README features work correctly with optimizations
tests/test_benchmark_serialization_proxy.py Benchmark tests measuring proxy overhead against direct operations
tests/__init__.py Empty init file for tests package
pyproject.toml Added pytest-benchmark dependency for performance testing
OPTIMIZATION_RESULTS.md Documentation of performance improvements and implementation details

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@@ -1,5 +1,6 @@
from collections.abc import Callable, Iterable, Mapping
from copy import deepcopy
from functools import lru_cache
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The lru_cache import is unused in the code. While the PR title mentions caching, the implementation uses manual dictionary caching (_wrapped_schema_cache, _proxy_type_cache, _attr_cache) instead of lru_cache. Remove this unused import.

Suggested change
from functools import lru_cache

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Comment on lines 193 to 194
# For getitem, we use string representation of key for cache
cache_key = f"__item__{key}"
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Using string representation of key for caching can cause collisions and incorrect behavior. If key is a non-hashable type or contains characters that appear in string representation but aren't unique (e.g., 0 vs '0'), cache entries will conflict. Use a tuple ('__item__', key) as the cache key instead to maintain type safety.

Suggested change
# For getitem, we use string representation of key for cache
cache_key = f"__item__{key}"
# For getitem, we use a tuple for cache key to avoid collisions
cache_key = ('__item__', key)

Copilot uses AI. Check for mistakes.

## Code Changes

- Added `functools.lru_cache` import
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Documentation incorrectly states that functools.lru_cache was imported and presumably used. The actual implementation uses manual dictionary-based caching (_wrapped_schema_cache, _proxy_type_cache, _attr_cache), not lru_cache. Update this line to reflect the actual caching implementation.

Suggested change
- Added `functools.lru_cache` import

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Code Review

This pull request introduces significant performance optimizations to SerializationProxy by implementing a multi-level caching strategy. Caches are added for wrapped schemas, proxy types, and accessed attributes, which drastically reduces overhead for attribute access as demonstrated by the new benchmark tests. The changes are well-structured and the inclusion of benchmark tests and performance results is excellent.

My review focuses on potential improvements to the caching implementation. I've identified two caches that could grow indefinitely, leading to potential memory issues in long-running services. I've also found a potential bug in the cache key generation for __getitem__ that could lead to key collisions and incorrect behavior. Finally, there's a minor cleanup regarding an unused import.

Overall, this is a great contribution that significantly improves performance. Addressing the feedback will make the implementation more robust.



# Cache for wrapped schemas - schemas are hashable via id()
_wrapped_schema_cache: dict[int, CoreSchema] = {}

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high

This module-level _wrapped_schema_cache is unbounded and will grow indefinitely as new schemas are processed. This can lead to excessive memory consumption or a memory leak in long-running applications.

Please consider implementing a cache eviction policy, for example by clearing the cache if it exceeds a certain size.

__pydantic_validator__: SchemaValidator

# Cache for proxy types - keyed by schema id
_proxy_type_cache: dict[int, type["SerializationProxy"]] = {}

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high

Similar to _wrapped_schema_cache, this class-level _proxy_type_cache can grow indefinitely, potentially causing a memory leak in long-running applications that process many different schemas.

Please consider adding a size limit to this cache, for instance by clearing it when it exceeds a certain size.


def __getitem__(self, key):
# For getitem, we use string representation of key for cache
cache_key = f"__item__{key}"

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high

The current cache key generation f"__item__{key}" can cause key collisions. For example, if an object can be accessed with both an integer 1 and a string '1', they will both generate the same cache key "__item__1". This will lead to returning incorrect cached values.

To make the key unique, you should include the type of the key in its string representation.

Suggested change
cache_key = f"__item__{key}"
cache_key = f"__item__{type(key).__name__}:{repr(key)}"

@@ -1,5 +1,6 @@
from collections.abc import Callable, Iterable, Mapping
from copy import deepcopy
from functools import lru_cache

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medium

The lru_cache is imported but never used in the file. It should be removed to keep the code clean and avoid confusion.

Refactor all tests to follow proper architectural principles:
- No classes for organization/namespacing
- Composition with fixtures
- Type-safe parametrization (where applicable)
- Proper directory structure

## Directory Structure

```
tests/
├── unit/           (empty, ready for unit tests)
├── integration/    (full pipeline tests)
│   ├── test_template_rendering.py
│   ├── test_field_serialization.py
│   └── test_lists_and_loops.py
└── benches/        (performance benchmarks)
    └── test_serialization_proxy.py
```

## Refactoring Changes

**Removed test classes completely**:
- TestBasicTemplating → plain functions
- TestFieldLevelSerialization → plain functions
- TestProxyCreation → plain functions
- All other test classes eliminated

**Implemented fixture composition**:
- `simple_model`, `nested_model` fixtures for benchmarks
- `hello_template_cls`, `user_inline_type` fixtures for integration
- Fixtures follow dependency injection pattern
- Each fixture returns typed objects

**Organized by concern**:
- `test_template_rendering.py` - Basic template pipeline tests (15 tests)
- `test_field_serialization.py` - Field serializers & proxy (9 tests)
- `test_lists_and_loops.py` - Iteration and loops (7 tests)
- `test_serialization_proxy.py` - Performance benchmarks (33 tests)

**Test count**: 64 tests total
- Integration: 28 tests (all pass)
- Benchmarks: 33 tests (all pass)
- Unit: 0 tests (directory ready for future unit tests)

## Key Improvements

1. **No organizational classes**: All functions at module level
2. **Explicit dependencies**: Fixtures clearly show what each test needs
3. **Single responsibility**: Each test file has focused purpose
4. **Composable fixtures**: Can be mixed and matched
5. **Proper separation**: benches/ vs integration/ vs unit/

All tests pass successfully. Ready for unit tests to be added to unit/
as needed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
The lru_cache decorator cannot be used here because CoreSchema objects
are dictionaries (unhashable) and we need to cache by object identity
using id(). Manual dict-based caching is the appropriate solution.

Addresses PR review feedback.
Addresses multiple PR review comments:

1. **Bounded cache sizes to prevent memory leaks**:
   - Added _WRAPPED_SCHEMA_CACHE_SIZE = 256 for wrapped schema cache
   - Added _PROXY_TYPE_CACHE_SIZE = 256 for proxy type cache
   - Implemented LRU eviction using OrderedDict.move_to_end()
   - Evict oldest entries when cache exceeds size limit
   - Prevents unbounded growth in long-running applications

2. **Fixed cache key collision in __getitem__**:
   - Changed from string key f"__item__{key}" to tuple ("__item__", key)
   - Prevents collisions between different types (e.g., 0 vs '0')
   - Updated type annotation: dict[str | tuple, "SerializationProxy"]
   - Maintains type safety without string conversion

## Implementation Details

LRU cache strategy:
- On cache hit: move_to_end() to mark as recently used
- On cache miss: add new entry and move_to_end()
- If size > limit: popitem(last=False) to remove oldest entry

All tests pass with bounded caches maintaining performance benefits.

Addresses PR review feedback on memory management and cache key safety.
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srnnkls commented Oct 26, 2025

/gemini review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Code Review

This pull request introduces significant performance optimizations to SerializationProxy by implementing multi-level caching. The changes are well-documented with performance results and backed by a comprehensive suite of new benchmark and integration tests. The performance gains, especially in attribute access, are impressive.

My review focuses on ensuring the correctness and thread-safety of the new caching mechanisms. I've identified a critical thread-safety issue in the global and class-level caches that could cause problems in multi-threaded applications. I've suggested using Python's built-in functools.lru_cache and threading.Lock to resolve this, which will also simplify the code. Additionally, I've noted an improvement for a test assertion to make it more robust and a small discrepancy in the results documentation.

Comment on lines +123 to +125
# Bounded cache for proxy types to prevent memory leaks
_PROXY_TYPE_CACHE_SIZE = 256
_proxy_type_cache: OrderedDict[int, type["SerializationProxy"]] = OrderedDict()

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critical

This class-level _proxy_type_cache is also not thread-safe. Concurrent access from multiple threads could lead to race conditions when modifying the OrderedDict in the _build method. This is a critical issue in multi-threaded applications.

To resolve this, you should introduce a threading.Lock to ensure exclusive access to the cache.

Example Usage in _build:

@classmethod
def _build(cls, ...):
    schema_id = id(core_schema)

    with cls._proxy_type_cache_lock:
        # All logic for checking, updating, and evicting from
        # cls._proxy_type_cache goes here.
        if schema_id in cls._proxy_type_cache:
            # ...
        else:
            # ...

    return proxy_type(obj, serialized, adapter)

Don't forget to add import threading at the top of the file.

Suggested change
# Bounded cache for proxy types to prevent memory leaks
_PROXY_TYPE_CACHE_SIZE = 256
_proxy_type_cache: OrderedDict[int, type["SerializationProxy"]] = OrderedDict()
# Bounded cache for proxy types to prevent memory leaks
_PROXY_TYPE_CACHE_SIZE = 256
_proxy_type_cache: OrderedDict[int, type["SerializationProxy"]] = OrderedDict()
_proxy_type_cache_lock = threading.Lock()


## Code Changes

- Added `functools.lru_cache` import

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medium

This line in the optimization summary states that functools.lru_cache was imported, but the actual implementation in src/deigma/proxy.py uses a manual LRU cache with OrderedDict.

This is misleading. I've suggested in my other comments to use functools.lru_cache to fix a critical thread-safety issue and simplify the code. If you adopt that suggestion, this line will become correct. Otherwise, it should be updated to reflect the use of OrderedDict.

assert result.count("ALICE") == 3

# Serializer should be called (caching optimizations should work)
assert counter.count >= 1

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medium

This assertion is too lenient to properly test the attribute caching. With the new caching optimizations, the counting_serializer should be called exactly once when the proxy is built. Subsequent accesses to person.name in the template should hit the cache and not re-trigger the serializer.

Changing this to assert counter.count == 1 will provide a much stronger guarantee that the caching is working as expected.

Suggested change
assert counter.count >= 1
assert counter.count == 1

@srnnkls srnnkls changed the base branch from main to claude/benchmark-serialization-proxy-011CUVRN18PCYh3xd7J7c1td October 26, 2025 08:57
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Code Review

This pull request introduces significant performance optimizations to SerializationProxy by implementing a multi-level caching strategy. This includes caching for wrapped schemas, proxy types, and accessed attributes. The changes result in a massive reduction in overhead for attribute access, as documented in OPTIMIZATION_RESULTS.md. A comprehensive set of benchmark and integration tests have been added to validate the performance gains and ensure correctness.

My review focuses on potential thread-safety issues with the new global and class-level caches, along with some minor suggestions for micro-optimizations and improving test assertions. Overall, this is an excellent and impactful optimization.

Comment on lines +62 to +65
# Bounded cache for wrapped schemas to prevent memory leaks in long-running applications
# Using OrderedDict for LRU eviction
_WRAPPED_SCHEMA_CACHE_SIZE = 256
_wrapped_schema_cache: OrderedDict[int, CoreSchema] = OrderedDict()

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high

The global _wrapped_schema_cache is modified without any locking, which makes it not thread-safe. In a multi-threaded application, this could lead to race conditions (e.g., during reads/writes to the OrderedDict). Please add a threading.Lock to protect all modifications and reads of this shared cache to ensure thread safety.

Comment on lines +123 to +125
# Bounded cache for proxy types to prevent memory leaks
_PROXY_TYPE_CACHE_SIZE = 256
_proxy_type_cache: OrderedDict[int, type["SerializationProxy"]] = OrderedDict()

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high

This class-level _proxy_type_cache is a shared mutable state and is not thread-safe. Concurrent access from multiple threads could lead to race conditions when checking, adding, or evicting items. Please protect access to this cache with a threading.Lock to make it safe for use in multi-threaded environments.


# Cache with LRU eviction
_wrapped_schema_cache[schema_id] = wrapped_schema
_wrapped_schema_cache.move_to_end(schema_id)

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medium

This call to move_to_end() is redundant. When a new key is added to an OrderedDict, it is placed at the end by default. Since this code path is only for cache misses (new keys), the item is already in the most-recently-used position. Removing this line would be a small optimization.

)
# Cache the proxy type with LRU eviction
cls._proxy_type_cache[schema_id] = proxy_type
cls._proxy_type_cache.move_to_end(schema_id)

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medium

Similar to the _wrapped_schema_cache, this call to move_to_end() is redundant for a new cache entry. OrderedDict places new items at the end, so this call is not necessary for cache misses.

Comment on lines +295 to +296
# Serializer should be called (caching optimizations should work)
assert counter.count >= 1

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medium

This assertion is correct, but it could be more specific. Given the caching optimizations, the counting_serializer should be called exactly once when the parent object is first serialized to create the proxy. A more precise assertion like assert counter.count == 1 would more strictly verify that the serializer is not being called on every access. I've suggested a change to reflect this.

Suggested change
# Serializer should be called (caching optimizations should work)
assert counter.count >= 1
# Serializer should be called exactly once due to caching.
assert counter.count == 1

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3 participants