pypa/pip

Performance Issue: Too many hashes in RequirementPreparer

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#12,589 opened on Mar 23, 2024

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help wantedtype: performance

Description

Description

RequirementPreparer hashes more than necessary. This leads to poor performance on large wheels in the GB size range.

A call to prepare_linked_requirement calls down to _checked_download_dir. https://github.com/pypa/pip/blob/f5e4ee104e7b171a7cfb2843c9c602abf7a4e346/src/pip/_internal/operations/prepare.py#L501

If the file exists in the download_dir, hashing is triggered. The file is marked as downloaded. https://github.com/pypa/pip/blob/f5e4ee104e7b171a7cfb2843c9c602abf7a4e346/src/pip/_internal/operations/prepare.py#L516

Then we head into _prepare_linked_requirement and eventually hash again. https://github.com/pypa/pip/blob/main/src/pip/_internal/operations/prepare.py#L612

Potential Fix

Files which have passed the hash check can be marked as such, to prevent rehashing.

Expected behavior

RequirementPreparer hashes each file at most once.

pip version

24.0

Python version

3.11

OS

Windows 10

How to Reproduce

Construct a RequirementPreparer supplied with a download_dir. Run prepare_linked_requirement() for a link available as a wheel in the download_dir.

Output

No response

Code of Conduct

Contributor guide

Tech stack
python
Domain
performancetooling
Issue type
performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Pythonfamiliarity with pip's source code
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the double hashing in pip's RequirementPreparer. Focus on the ` checked download dir` and ` prepare linked requirement` methods in `src/pip/ internal/operations/prepare.py`. The issue suggests marking files that have passed the hash check to avoid rehashing. Implement a mechanism to track hashed files, possibly using a set or flag. Ensure the change does not affect downstream logic.
Performance Issue: Too many hashes in RequirementPreparer · pypa/pip#12589 | Good First Issue