How SELECT statement can cause disk write IO - generate data

generate_data.py

import random

NUM_AUTHORS = 10000000
NUM_BOOKS = 20000000

# Any author can wite any book
author_sql = """INSERT INTO author (id, name) values ({i}, 'author_{i}');\n"""
book_sql = """INSERT INTO book (title, author_id) values ('title_{i}', {author_id});\n"""

data_file = open('data.sql', 'w')

data_file.write('BEGIN;\n')
for i in range(NUM_AUTHORS):
    data_file.write(author_sql.format(i=i+1))
data_file.write('COMMIT;\n')

data_file.write('BEGIN;\n')
for i in range(NUM_BOOKS):
    author_id = random.randint(1, NUM_AUTHORS)
    data_file.write(book_sql.format(i=i, author_id=author_id))
data_file.write('COMMIT;\n')

data_file.close()