PYTHON-5679 Optimize ObjectId.__str__()

[adamchainz]

Changes in this PR

Like #2656, I spotted this function taking ~0.9% of request time in a project using mongoengine.

bytes.hex() was added in Python 3.5 and does the same as binascii.hexlify(...).decode() but faster, so I've replaced it here. (The binascii.hexlify() docs also now point to bytes.hex() as a faster alternative.)

Test Plan

Benchmarked again using richbench with the below script.

bench_objectid_str.py

from __future__ import annotations

import binascii
import os

class ObjectIdBefore:
    __slots__ = ("__id",)

    def __init__(self) -> None:
        self.__id = os.urandom(12)

    def __str__(self) -> str:
        return binascii.hexlify(self.__id).decode()

class ObjectIdAfter:
    __slots__ = ("__id",)

    def __init__(self) -> None:
        self.__id = os.urandom(12)

    def __str__(self) -> str:
        return self.__id.hex()

test_oids_before = [ObjectIdBefore() for _ in range(100)]
test_oids_after = [ObjectIdAfter() for _ in range(100)]

def bench_str_before():
    for oid in test_oids_before:
        for _ in range(100_000):
            str(oid)

def bench_str_after():
    for oid in test_oids_after:
        for _ in range(100_000):
            str(oid)

__benchmarks__ = [
    (bench_str_before, bench_str_after, "str(ObjectId) - hex conversion"),
]

Results show a ~1.4x speedup:

$ uvx -p 3.13 richbench .
                                            Benchmarks, repeat=5, number=5
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┓
┃                      Benchmark ┃ Min     ┃ Max     ┃ Mean    ┃ Min (+)         ┃ Max (+)         ┃ Mean (+)        ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━┩
│ str(ObjectId) - hex conversion │ 3.000   │ 3.061   │ 3.019   │ 2.169 (1.4x)    │ 2.231 (1.4x)    │ 2.196 (1.4x)    │
└────────────────────────────────┴─────────┴─────────┴─────────┴─────────────────┴─────────────────┴─────────────────┘

Checklist

Checklist for Author

• Did you update the changelog (if necessary)?
• Is there test coverage?
• Is any followup work tracked in a JIRA ticket? If so, add link(s).

Checklist for Reviewer

• Does the title of the PR reference a JIRA Ticket?
• Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
• Is all relevant documentation (README or docstring) updated?

[blink1073]

LGTM!