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Stored (uncompressed) ZipExtFile in zipfile can be seekable at lower cost #88339

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JuniorJPDJ mannequin opened this issue May 19, 2021 · 2 comments
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Stored (uncompressed) ZipExtFile in zipfile can be seekable at lower cost #88339

JuniorJPDJ mannequin opened this issue May 19, 2021 · 2 comments
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@gpshead
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3.12 stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@JuniorJPDJ
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@JuniorJPDJ JuniorJPDJ mannequin commented May 19, 2021

BPO 44173
Nosy @Yhg1s, @gpshead, @serhiy-storchaka, @JuniorJPDJ
PRs
  • #26227
  • #27737
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/gpshead'
closed_at = None
created_at = <Date 2021-05-19.02:28:39.857>
labels = ['type-feature', 'library', '3.11']
title = 'Stored (uncompressed) ZipExtFile in zipfile can be seekable at lower cost'
updated_at = <Date 2021-08-18.17:30:30.110>
user = 'https://github.com/JuniorJPDJ'

    bugs.python.org fields:

    activity = <Date 2021-08-18.17:30:30.110>
actor = 'gregory.p.smith'
assignee = 'gregory.p.smith'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-05-19.02:28:39.857>
creator = 'juniorjpdj'
dependencies = []
files = []
hgrepos = []
issue_num = 44173
keywords = ['patch']
message_count = 1.0
messages = ['393918']
nosy_count = 5.0
nosy_names = ['twouters', 'gregory.p.smith', 'alanmcintyre', 'serhiy.storchaka', 'juniorjpdj']
pr_nums = ['26227', '27737']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44173'
versions = ['Python 3.11']
    @JuniorJPDJ
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    @JuniorJPDJ JuniorJPDJ mannequin commented May 19, 2021

    At the moment stored ZipExtFile is being read to the place of seek like all other compressed variants.
    It's not needed as it's possible to freely seek uncompressed file inside zip without this penalty.

    Lots of apps depend on ZipExtFile seeking ability and it would lower performance and IO penalty significantly.

    I've POC patch created.
    It disables CRC checking after first seek as it's impossible to check CRC if we are not reading whole file.

    @JuniorJPDJ JuniorJPDJ mannequin added 3.11 stdlib Python modules in the Lib dir type-feature A feature request or enhancement labels May 19, 2021
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
    @JuniorJPDJ JuniorJPDJ mannequin mentioned this issue Apr 18, 2022
    Merged
    gpshead pushed a commit that referenced this issue Aug 6, 2022
    @JuniorJPDJ
    gh-88339: enable fast seeking of uncompressed unencrypted zipfile.Zip…
    330f1d5 
    …ExtFile (GH-27737)

Avoid reading all of the intermediate data in uncompressed items in a zip file when the user seeks forward.

Contributed by: @JuniorJPDJ
    @gpshead gpshead added 3.12 and removed 3.11 labels Aug 6, 2022
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    @gpshead gpshead commented Aug 6, 2022

    merged for 3.12. thanks for the contribution!

    @gpshead gpshead closed this as completed Aug 6, 2022
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    Labels
    3.12 stdlib Python modules in the Lib dir type-feature A feature request or enhancement
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    Zipfile issues
    Status: Done
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