⚡️ Speed up method JSONField.get_transform by 9%

[codeflash-ai]

📄 9% (0.09x) speedup for JSONField.get_transform in django/db/models/fields/json.py

⏱️ Runtime : 1.70 milliseconds → 1.55 milliseconds (best of 108 runs)

📝 Explanation and details

The optimization replaces super().get_transform(name) with Field.get_transform(self, name) in the get_transform method. This change bypasses Python's method resolution order (MRO) machinery by directly calling the parent class method instead of using the super() builtin.

Key Performance Improvement:

• super() involves runtime MRO traversal and method lookup overhead
• Direct class method calls (Field.get_transform(self, name)) skip this dynamic resolution
• The line profiler shows the critical line improved from 4169.2ns per hit to 4011.8ns per hit (3.8% faster per call)

Why This Works:
Since JSONField inherits from CheckFieldDefaultMixin and Field, and CheckFieldDefaultMixin doesn't override get_transform, the method resolution would naturally find Field.get_transform anyway. The direct call eliminates the unnecessary MRO traversal step.

Test Case Performance:
The optimization shows consistent improvements across all test scenarios:

• Simple key lookups: 1-8% faster
• Bulk operations: Up to 10% faster (test with 999 keys)
• Edge cases (None, numeric, special chars): 1-7% faster
• Only minimal regressions in 2-3 cases with complex object keys

This optimization is particularly effective for high-frequency method calls in Django ORM query processing, where get_transform may be called repeatedly during JSON field operations.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 1148 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	75.0%

🌀 Generated Regression Tests and Runtime

import pytest  # used for our unit tests
from django.db.models.fields.json import JSONField


# function to test
class DummyField:
    """Dummy superclass to simulate Field.get_transform."""
    def get_transform(self, name):
        # Simulate: only 'upper' is supported by super
        if name == 'upper':
            return lambda x: str(x).upper()
        return None

class KeyTransformFactory:
    """Dummy transform factory, returns a function that extracts the key from a dict."""
    def __init__(self, key):
        self.key = key

    def __call__(self, value):
        # Return value[key] if dict, else raise
        if isinstance(value, dict):
            return value.get(self.key, None)
        raise TypeError("Value must be a dict.")
from django.db.models.fields.json import JSONField

# unit tests

# --- Basic Test Cases ---

def test_superclass_transform_found():
    """Test: get_transform returns superclass transform when available."""
    field = JSONField()
    codeflash_output = field.get_transform('upper'); transform = codeflash_output # 6.64μs -> 6.48μs (2.48% faster)

def test_key_transform_factory_basic():
    """Test: get_transform returns KeyTransformFactory for missing transforms."""
    field = JSONField()
    codeflash_output = field.get_transform('foo'); transform = codeflash_output # 4.76μs -> 4.68μs (1.71% faster)
    # Should extract 'foo' from dict
    d = {'foo': 123, 'bar': 456}

def test_key_transform_factory_missing_key():
    """Test: KeyTransformFactory returns None for missing key."""
    field = JSONField()
    codeflash_output = field.get_transform('baz'); transform = codeflash_output # 4.51μs -> 4.34μs (3.84% faster)
    d = {'foo': 123}


def test_get_transform_empty_string_key():
    """Test: KeyTransformFactory with empty string as key."""
    field = JSONField()
    codeflash_output = field.get_transform(''); transform = codeflash_output # 6.54μs -> 6.59μs (0.880% slower)
    d = {'': 'empty'}
    # Key not present
    d = {'foo': 1}

def test_get_transform_none_key():
    """Test: KeyTransformFactory with None as key."""
    field = JSONField()
    codeflash_output = field.get_transform(None); transform = codeflash_output # 5.10μs -> 4.79μs (6.34% faster)
    d = {None: 'noneval', 'foo': 2}
    # Key not present
    d = {'foo': 2}

def test_get_transform_numeric_key():
    """Test: KeyTransformFactory with numeric key."""
    field = JSONField()
    codeflash_output = field.get_transform(42); transform = codeflash_output # 4.43μs -> 4.35μs (1.86% faster)
    d = {42: 'answer', 'foo': 2}
    # Key not present
    d = {'foo': 2}

def test_encoder_decoder_validation():
    """Test: encoder and decoder must be callable if provided."""
    # Encoder not callable
    with pytest.raises(ValueError):
        JSONField(encoder='not_callable')
    # Decoder not callable
    with pytest.raises(ValueError):
        JSONField(decoder=123)
    # Both callable
    field = JSONField(encoder=lambda x: x, decoder=lambda x: x)

def test_key_transform_factory_with_mutable_key():
    """Test: KeyTransformFactory with tuple key (hashable, but not string/int)."""
    field = JSONField()
    key = ('a', 1)
    codeflash_output = field.get_transform(key); transform = codeflash_output # 4.93μs -> 4.55μs (8.21% faster)
    d = {('a', 1): 'tupleval'}
    # Key not present
    d = {'foo': 2}


def test_key_transform_factory_large_dict():
    """Test: KeyTransformFactory with large dictionary."""
    field = JSONField()
    key = 'bigkey'
    # Create a dict with 999 elements
    d = {f'key{i}': i for i in range(999)}
    d['bigkey'] = 'largevalue'
    codeflash_output = field.get_transform(key); transform = codeflash_output # 7.20μs -> 6.98μs (3.07% faster)

def test_key_transform_factory_many_keys():
    """Test: get_transform with many different keys in succession."""
    field = JSONField()
    d = {f'k{i}': i for i in range(999)}
    for i in range(999):
        key = f'k{i}'
        codeflash_output = field.get_transform(key); transform = codeflash_output # 1.44ms -> 1.31ms (10.0% faster)


def test_superclass_transform_many_calls():
    """Test: get_transform returns correct transform from superclass for many calls."""
    field = JSONField()
    for i in range(100):
        codeflash_output = field.get_transform('upper'); transform = codeflash_output # 151μs -> 138μs (8.87% faster)

def test_key_transform_factory_performance():
    """Test: KeyTransformFactory performance with dict of 999 elements."""
    import time
    field = JSONField()
    key = 'key500'
    d = {f'key{i}': i for i in range(999)}
    codeflash_output = field.get_transform(key); transform = codeflash_output # 4.64μs -> 4.36μs (6.45% faster)
    start = time.time()
    result = transform(d)
    duration = time.time() - start
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
import pytest
from django.db.models.fields.json import JSONField


# function to test (standalone, as we don't have the full Django ORM and super())
class KeyTransformFactory:
    def __init__(self, name):
        self.name = name

class DummySuper:
    # Simulate the super().get_transform behavior
    def get_transform(self, name):
        # For demonstration, only 'existing' returns a dummy transform
        if name == "existing":
            return "super_transform"
        return None
from django.db.models.fields.json import JSONField

# unit tests

# 1. Basic Test Cases

def test_get_transform_returns_super_transform():
    # Should return the super's transform if present
    field = JSONField()
    codeflash_output = field.get_transform("existing"); result = codeflash_output # 4.52μs -> 4.28μs (5.78% faster)

def test_get_transform_returns_keytransformfactory():
    # Should return KeyTransformFactory if super's transform is not present
    field = JSONField()
    codeflash_output = field.get_transform("foo"); result = codeflash_output # 4.20μs -> 3.89μs (8.00% faster)

def test_get_transform_with_numeric_key():
    # Should work with numeric string keys
    field = JSONField()
    codeflash_output = field.get_transform("123"); result = codeflash_output # 4.11μs -> 4.01μs (2.47% faster)

def test_get_transform_with_empty_string_key():
    # Should work with empty string key
    field = JSONField()
    codeflash_output = field.get_transform(""); result = codeflash_output # 4.05μs -> 3.92μs (3.42% faster)

def test_get_transform_with_special_characters():
    # Should handle keys with special characters
    field = JSONField()
    special_key = "!@#$%^&*()_+-=[]{}|;':,./<>?"
    codeflash_output = field.get_transform(special_key); result = codeflash_output # 4.00μs -> 3.94μs (1.60% faster)

# 2. Edge Test Cases

def test_get_transform_with_none_key():
    # Should handle None as key gracefully
    field = JSONField()
    codeflash_output = field.get_transform(None); result = codeflash_output # 4.14μs -> 4.06μs (1.97% faster)

def test_get_transform_with_long_string_key():
    # Should handle long string keys
    field = JSONField()
    long_key = "a" * 500
    codeflash_output = field.get_transform(long_key); result = codeflash_output # 4.09μs -> 3.85μs (6.35% faster)

def test_get_transform_with_tuple_key():
    # Should handle tuple as key
    field = JSONField()
    tuple_key = ("tuple", "key")
    codeflash_output = field.get_transform(tuple_key); result = codeflash_output # 4.03μs -> 4.16μs (3.10% slower)

def test_get_transform_with_int_key():
    # Should handle int as key
    field = JSONField()
    int_key = 42
    codeflash_output = field.get_transform(int_key); result = codeflash_output # 3.98μs -> 3.83μs (3.68% faster)

def test_get_transform_with_float_key():
    # Should handle float as key
    field = JSONField()
    float_key = 3.1415
    codeflash_output = field.get_transform(float_key); result = codeflash_output # 4.38μs -> 4.07μs (7.57% faster)

def test_get_transform_with_bool_key():
    # Should handle bool as key
    field = JSONField()
    bool_key = True
    codeflash_output = field.get_transform(bool_key); result = codeflash_output # 3.95μs -> 3.81μs (3.43% faster)

def test_get_transform_with_object_key():
    # Should handle object as key
    field = JSONField()
    class Dummy: pass
    obj_key = Dummy()
    codeflash_output = field.get_transform(obj_key); result = codeflash_output # 4.02μs -> 4.10μs (1.95% slower)




def test_get_transform_large_key_size():
    # Should handle a very large key string (edge of reasonable size)
    field = JSONField()
    large_key = "x" * 1000
    codeflash_output = field.get_transform(large_key); result = codeflash_output # 6.79μs -> 6.71μs (1.10% faster)

To edit these changes git checkout codeflash/optimize-JSONField.get_transform-mhcz9c4p and push.