⚡️ Speed up method MigrationQuestioner.ask_not_null_alteration by 6%

[codeflash-ai]

📄 6% (0.06x) speedup for MigrationQuestioner.ask_not_null_alteration in django/db/migrations/questioner.py

⏱️ Runtime : 337 microseconds → 319 microseconds (best of 161 runs)

📝 Explanation and details

The optimization replaces defaults or {} and specified_apps or set() with explicit None checks using if x is not None else ... in the __init__ method.

Key Change: Instead of relying on Python's truthiness evaluation (where or creates new objects even when the left operand is falsy but not None), the optimized version only creates new empty containers when the parameter is actually None.

Why It's Faster: The or operator always evaluates both operands and creates new objects ({} and set()) on every instantiation. The explicit None check avoids unnecessary object creation when non-None values are passed, even if they're falsy (like empty dicts or sets). This reduces memory allocation overhead and interpreter work.

Performance Pattern: The optimization shows consistent gains in scenarios with multiple instantiations (test_large_scale_many_calls: 5.5-7.1% faster, test_returns_none_with_multiple_instances: 6.13% faster) where the reduced object creation accumulates. Individual method calls to ask_not_null_alteration show mixed but generally positive results, likely due to reduced initialization overhead when the questioner instances are created during testing.

This optimization is particularly effective for classes that are frequently instantiated, as it eliminates redundant object creation during initialization.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 3294 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Generated Regression Tests and Runtime

import pytest  # used for our unit tests
from django.db.migrations.questioner import MigrationQuestioner

# unit tests

# ----------------------------
# Basic Test Cases
# ----------------------------

def test_basic_typical_names():
    """Test with typical field and model names."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('age', 'Person'); result = codeflash_output # 241ns -> 245ns (1.63% slower)

def test_basic_empty_strings():
    """Test with empty strings for field and model names."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('', ''); result = codeflash_output # 238ns -> 241ns (1.24% slower)

def test_basic_numeric_names():
    """Test with numeric strings as field and model names."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('123', '456'); result = codeflash_output # 239ns -> 240ns (0.417% slower)

def test_basic_special_characters():
    """Test with special characters in field and model names."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('field@#, 'model*&^'); result = codeflash_output # 245ns -> 239ns (2.51% faster)

def test_basic_unicode_names():
    """Test with unicode characters in field and model names."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('名字', '模型'); result = codeflash_output # 229ns -> 242ns (5.37% slower)

# ----------------------------
# Edge Test Cases
# ----------------------------

def test_edge_none_field_name():
    """Test with None as field_name."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(None, 'Model'); result = codeflash_output # 229ns -> 238ns (3.78% slower)

def test_edge_none_model_name():
    """Test with None as model_name."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('field', None); result = codeflash_output # 234ns -> 233ns (0.429% faster)

def test_edge_both_none():
    """Test with both field_name and model_name as None."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(None, None); result = codeflash_output # 240ns -> 235ns (2.13% faster)

def test_edge_boolean_field_name():
    """Test with boolean as field_name."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(True, 'Model'); result = codeflash_output # 235ns -> 232ns (1.29% faster)

def test_edge_boolean_model_name():
    """Test with boolean as model_name."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('field', False); result = codeflash_output # 227ns -> 220ns (3.18% faster)

def test_edge_integer_field_name():
    """Test with integer as field_name."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(123, 'Model'); result = codeflash_output # 234ns -> 231ns (1.30% faster)

def test_edge_integer_model_name():
    """Test with integer as model_name."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration('field', 456); result = codeflash_output # 224ns -> 215ns (4.19% faster)

def test_edge_long_string_names():
    """Test with very long strings for field and model names."""
    long_field = 'f' * 1000
    long_model = 'm' * 1000
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(long_field, long_model); result = codeflash_output # 223ns -> 220ns (1.36% faster)

def test_edge_tuple_inputs():
    """Test with tuple inputs."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(('field',), ('model',)); result = codeflash_output # 224ns -> 213ns (5.16% faster)

def test_edge_list_inputs():
    """Test with list inputs."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(['field'], ['model']); result = codeflash_output # 227ns -> 230ns (1.30% slower)

def test_edge_dict_inputs():
    """Test with dict inputs."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration({'field': 1}, {'model': 2}); result = codeflash_output # 248ns -> 248ns (0.000% faster)

def test_edge_object_inputs():
    """Test with arbitrary objects as inputs."""
    class Dummy: pass
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(Dummy(), Dummy()); result = codeflash_output # 251ns -> 235ns (6.81% faster)

# ----------------------------
# Large Scale Test Cases
# ----------------------------

@pytest.mark.parametrize("field_name,model_name", [
    (f"field_{i}", f"model_{i}") for i in range(100)
])
def test_large_scale_varied_names(field_name, model_name):
    """Test with 100 different field/model name pairs."""
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(field_name, model_name); result = codeflash_output # 23.1μs -> 23.4μs (1.57% slower)

def test_large_scale_long_names():
    """Test with 1000-character-long field and model names."""
    field_name = 'f' * 1000
    model_name = 'm' * 1000
    q = MigrationQuestioner()
    codeflash_output = q.ask_not_null_alteration(field_name, model_name); result = codeflash_output # 232ns -> 235ns (1.28% slower)

def test_large_scale_many_calls():
    """Test calling the function 1000 times with unique inputs."""
    q = MigrationQuestioner()
    for i in range(1000):
        field_name = f"field_{i}"
        model_name = f"model_{i}"
        codeflash_output = q.ask_not_null_alteration(field_name, model_name); result = codeflash_output # 101μs -> 96.2μs (5.50% faster)

# ----------------------------
# Additional Robustness Tests
# ----------------------------

def test_defaults_and_specified_apps():
    """Test that defaults and specified_apps do not affect behavior."""
    q = MigrationQuestioner(defaults={'foo': 'bar'}, specified_apps={'app1', 'app2'}, dry_run=True)
    codeflash_output = q.ask_not_null_alteration('field', 'model'); result = codeflash_output # 274ns -> 278ns (1.44% slower)

def test_multiple_instances_independence():
    """Test that multiple instances do not interfere with each other."""
    q1 = MigrationQuestioner()
    q2 = MigrationQuestioner(defaults={'x': 1})
    codeflash_output = q1.ask_not_null_alteration('a', 'b') # 251ns -> 269ns (6.69% slower)
    codeflash_output = q2.ask_not_null_alteration('c', 'd') # 170ns -> 164ns (3.66% faster)
# 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.migrations.questioner import MigrationQuestioner

# unit tests

# 1. Basic Test Cases

def test_returns_none_with_normal_field_and_model():
    """Test that the method always returns None for typical field and model names."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("username", "User"); result = codeflash_output # 230ns -> 223ns (3.14% faster)

def test_returns_none_with_numeric_field_and_model():
    """Test with numeric field and model names."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("field123", "Model456"); result = codeflash_output # 224ns -> 227ns (1.32% slower)

def test_returns_none_with_underscore_field_and_model():
    """Test with underscores in field and model names."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("first_name", "UserProfile"); result = codeflash_output # 235ns -> 225ns (4.44% faster)

def test_returns_none_with_empty_strings():
    """Test with empty strings as field and model names."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("", ""); result = codeflash_output # 234ns -> 229ns (2.18% faster)

# 2. Edge Test Cases

def test_returns_none_with_none_field_and_model():
    """Test with None passed as field and model names."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration(None, None); result = codeflash_output # 233ns -> 225ns (3.56% faster)

def test_returns_none_with_special_characters():
    """Test with special characters in field and model names."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("@field!", "#Model$"); result = codeflash_output # 238ns -> 233ns (2.15% faster)

def test_returns_none_with_long_field_and_model_names():
    """Test with very long field and model names."""
    mq = MigrationQuestioner()
    long_field = "f" * 255
    long_model = "M" * 255
    codeflash_output = mq.ask_not_null_alteration(long_field, long_model); result = codeflash_output # 225ns -> 228ns (1.32% slower)

def test_returns_none_with_whitespace_only():
    """Test with whitespace-only strings."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("   ", "   "); result = codeflash_output # 224ns -> 241ns (7.05% slower)

def test_returns_none_with_mixed_types():
    """Test with non-string types as arguments."""
    mq = MigrationQuestioner()
    # int, float, list, dict, bool
    codeflash_output = mq.ask_not_null_alteration(123, 456) # 219ns -> 230ns (4.78% slower)
    codeflash_output = mq.ask_not_null_alteration(12.34, 56.78) # 160ns -> 190ns (15.8% slower)
    codeflash_output = mq.ask_not_null_alteration([1,2], {"a": 1}) # 137ns -> 140ns (2.14% slower)
    codeflash_output = mq.ask_not_null_alteration(True, False) # 111ns -> 107ns (3.74% faster)

def test_returns_none_with_unicode_characters():
    """Test with unicode characters in field and model names."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("имя", "Пользователь"); result = codeflash_output # 226ns -> 230ns (1.74% slower)

# 3. Large Scale Test Cases

def test_returns_none_many_unique_calls():
    """Test the function with a large number of unique field/model name pairs."""
    mq = MigrationQuestioner()
    for i in range(1000):
        field = f"field_{i}"
        model = f"Model_{i}"
        codeflash_output = mq.ask_not_null_alteration(field, model) # 100μs -> 94.3μs (6.38% faster)

def test_returns_none_with_large_strings():
    """Test with very large string arguments."""
    mq = MigrationQuestioner()
    large_field = "f" * 1000
    large_model = "M" * 1000
    codeflash_output = mq.ask_not_null_alteration(large_field, large_model) # 259ns -> 280ns (7.50% slower)

def test_returns_none_with_various_types_in_bulk():
    """Test with a mix of types in a loop to check robustness."""
    mq = MigrationQuestioner()
    test_cases = [
        (None, None),
        ("", ""),
        ("f", "M"),
        ("f"*100, "M"*100),
        (123, "Model"),
        ("field", 456),
        ([], {}),
        (True, False),
        ("имя", "Пользователь"),
        ("@field!", "#Model$"),
    ]
    for field, model in test_cases * 100:  # 1000 total calls
        codeflash_output = mq.ask_not_null_alteration(field, model) # 102μs -> 95.6μs (7.10% faster)

# 4. Additional Edge Cases for Mutation Testing

def test_returns_none_with_swapped_arguments():
    """Test that argument order does not affect return value."""
    mq = MigrationQuestioner()
    codeflash_output = mq.ask_not_null_alteration("User", "username") # 274ns -> 255ns (7.45% faster)

def test_returns_none_with_defaulted_init():
    """Test that defaults, specified_apps, dry_run do not affect return value."""
    mq = MigrationQuestioner(defaults={"a": 1}, specified_apps={"app"}, dry_run=True)
    codeflash_output = mq.ask_not_null_alteration("field", "model") # 253ns -> 269ns (5.95% slower)

def test_returns_none_with_multiple_instances():
    """Test that multiple instances behave identically."""
    for _ in range(10):
        mq = MigrationQuestioner()
        codeflash_output = mq.ask_not_null_alteration("field", "model") # 1.23μs -> 1.16μs (6.13% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-MigrationQuestioner.ask_not_null_alteration-mh6lydvt and push.