Evaluate usage of mmap

[mkrd]

mmap could greatly improve the performance of .at(…, key=…).session()

• https://stackoverflow.com/questions/5917047/delete-insert-data-in-mmaped-file
• https://stackoverflow.com/questions/50466557/python-write-content-into-existing-file
• https://stackoverflow.com/questions/64145647/why-is-mmap-in-python-so-slow

[mkrd]

import time
import mmap

def naive_insert_at_beginning():
    t1 = time.monotonic()
    with open("ddb_storage/users copy.json", "r+b") as f:
        data = f.read()
        f.seek(0)
        f.write(b"aaaa" + data)
        f.flush()

    t2 = time.monotonic()
    print(f"Time taken: {(t2 - t1) * 1000}ms")

# naive_insert_at_beginning()

def mmap_insert_at_beginning():
    t1 = time.monotonic()
    append_str = b"dddd"
    with open("ddb_storage/users copy.json", "a+b") as f:
        f.seek(0, 2)
        f.write(append_str)
        f.flush()

        with mmap.mmap(f.fileno(), 0, flags=mmap.MAP_PRIVATE, ) as m:
            m.move(0, 4, len(m) - 4)
            m.seek(0)
            m.write(append_str)
            m.flush()

    t2 = time.monotonic()
    print(f"Time taken: {(t2 - t1) * 1000}ms")

mmap_insert_at_beginning()