Simulate Shard Key Cardinality in Python

import random
import string

def calculate_cardinality(values):
    """Return the number of distinct values in the given list."""
    return len(set(values))

def generate_mock_data(num_records, cardinality):
    """Generate mock records for a shard key with given cardinality."""
    possible_keys = [f"key_{i:04d}" for i in range(cardinality)]
    return [random.choice(possible_keys) for _ in range(num_records)]

def evaluate_shard_key(cardinality, num_records=10000):
    """Simulate distribution of a shard key across records."""
    records = generate_mock_data(num_records, cardinality)
    distinct = calculate_cardinality(records)
    distribution = {}
    for key in records:
        distribution[key] = distribution.get(key, 0) + 1

    avg_per_shard = num_records / distinct
    return {
        "requested_cardinality": cardinality,
        "actual_distinct": distinct,
        "total_records": num_records,
        "avg_records_per_key": round(avg_per_shard, 2),
        "max_records_for_single_key": max(distribution.values()),
        "min_records_for_single_key": min(distribution.values()),
    }

if __name__ == "__main__":
    random.seed(42)  # deterministic output
    for card in [10, 100, 1000]:
        result = evaluate_shard_key(card)
        print(f"Cardinality={card}: {result}")