Reference library

Database scaling & optimization

Indexing, connection pooling, read replicas, query tuning, and throughput-aware SQL.

3 matches

How to Explain SQLite Query Plans in Python

Build a Python function that runs EXPLAIN QUERY PLAN on SQLite in-memory tables and prints the optimizer's execution plan for any SELECT statement.

sqlite query-plan optimization

Python

import sqlite3

def explain_query(sql: str) -> str:
    """Return the SQLite query plan for the given SQL statement."""
    conn = sqlite3.connect(":memory:")
    cursor = conn.cursor()
    
    # Create sample data for a realistic plan
    cursor.execute("CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT)")
    c…

14 0 Open

Database scaling & optimization easy

How to Mock a Function Call in Python with unittest.mock

Use unittest.mock.Mock to wrap a function and spy on its call count and arguments in Python.

mock unittest spy

Python

import random
from unittest.mock import Mock, patch


def select_n_plus_one(numbers: list[int]) -> int:
    """Return the first number that appears more than once, if any."""
    seen = set()
    for num in numbers:
        if num in seen:
            return num
        seen.add(num)
    return -1


def detect_mock(se…

14 0 Open

Database scaling & optimization easy

Rebalance Shard Ranges Across Nodes in Python

A mock rebalancing function that shuffles shard ranges and distributes them evenly across nodes using round-robin assignment.

sharding rebalancing dataclass

Python

import random
from dataclasses import dataclass

@dataclass
class Shard:
    id: int
    start: int
    end: int

def rebalance_shards(shards: list[Shard], node_count: int) -> dict[int, list[Shard]]:
    """Mock rebalancing of shard ranges across nodes."""
    all_ranges = [(s.start, s.end) for s in shards]
    random…

11 0 Open

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