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feature(stores): draft zip file store specification #311

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feature(stores): draft zip file store specification #311

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jhamman
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@jhamman jhamman commented Sep 11, 2024

This is a working draft of the v3 ZIP file store specification.

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@jhamman jhamman mentioned this pull request Sep 11, 2024
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jhamman
jhamman commented Sep 11, 2024
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docs/v3/stores/zipfile/v1.0.rst
Comment on lines +88 to +90
* Delete a file.

* Delete a directory.
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See #103

@joshmoore
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In my experience, the root of the zip is one of the trickiest parts for data creators (and I assume implementers) to get right, e.g.,

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cc: @DennisHeimbigner

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zoj613 commented Sep 11, 2024

How useful is a ZipStore in practice? Are there a lot of use cases for it? Given how limited it is (no rename/deletion, etc) I am wondering if its worth having a spec for it

@DennisHeimbigner
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I have support equivalent to zipstore in nczarr in the netcdf-c library. I agree that it does not appear to be
very useful, but the basic idea behind it is reasonable: a single file containing a complete zarr file tree,
and using compression the component files to save space.
Personally, I think that using a single file file system (SFFS) with added compression makes more sense.
There are several implementations available, and it is easy enough to write your own,

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jhamman commented Sep 12, 2024 •
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In my experience, the root of the zip is one of the trickiest parts for data creators (and I assume implementers) to get right...

@joshmoore - do you have suggestions for the spec document that would make this clearer?

@zoj613 and @DennisHeimbigner - let's try to avoid making this about alternatives to the ZIP store concept. There are practical reasons to add this (Zarr-Python has long supported a ZIP store interface).

Remember, Zarr can support many storage backends. If there are alternatives to experiment with, let's do that in a separate issue.

@DennisHeimbigner - I would like to get your feedback on the spec as written. Is it aligned with your netcdf-c implementation?

zoj613
zoj613 reviewed Sep 12, 2024
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docs/v3/stores/zipfile/v1.0.rst
Comment on lines +107 to +111
* ``get(key) -> value`` : Read and return the contents of the object at
within the archive at path ``key``.

* ``set(key, value)`` : Write ``value`` as the contents of the file at
into the archive at path ``key .
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Is the use of at within and at into in these lines intentional? Sounds like a typo

@LDeakin LDeakin mentioned this pull request Sep 12, 2024
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@joshmoore - do you have suggestions for the spec document that would make this clearer?

Thoughts that I have revolving in my head that include:

  • is it really a store spec or is it a format spec?
  • for the format, the most important item I know of is "don't include the top-level directory" (though I have run into some complaints about that from various repositories, since the behavior differs between implementations, e.g. on Windows)
  • for v2, I fully see getting this written down ASAP; for v3, I wonder if a general "archival" format that can be extended for, say, zip/tar/whatever wouldn't be something to consider

jhamman
jhamman commented Sep 29, 2024
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docs/v3/stores/zipfile/v1.0.rst
Comment on lines +63 to +64
* Each key has a name (sequence of characters) and contents
(sequence of bytes).
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Note that the keys are relative paths (not prefixed with a /).

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for the format, the most important item I know of is "don't include the top-level directory" (though I have run into some complaints about that from various repositories, since the behavior differs between implementations, e.g. on Windows)

I think I have always used either linux zip or cygwin zip to create zarr zip files. What native windows program could I use to create a pure windows zip file?
As for the top-level directory, I think it is better to always include it. I say this so that my rule holds, namely:
1.unzipping a zip store creates a directory tree usable by the zarr directory tree storage manager.
2. zipping a zarr directory tree creates a zip store conforming to the proposed zip spec.

@joshmoore joshmoore mentioned this pull request Oct 4, 2024
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jhamman commented Oct 7, 2024

I think I have always used either linux zip or cygwin zip to create zarr zip files. What native windows program could I use to create a pure windows zip file?

🤷

As for the top-level directory, I think it is better to always include it. I say this so that my rule holds, namely:
1.unzipping a zip store creates a directory tree usable by the zarr directory tree storage manager.
2. zipping a zarr directory tree creates a zip store conforming to the proposed zip spec.

👍

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A few downsides of adding the directory:

  • It's a change from v2 😄 though that can be handled.
  • You must know/lookup that value before you open the zip.
  • What is the behavior if there are multiple .zarr directories within the zip?

zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
366b728 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
4c64750 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
514167b 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
@zoj613 zoj613 mentioned this pull request Nov 6, 2024
Open
zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
4508108 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
1766416 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
772f3d3 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
76dd687 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
zoj613 added a commit to zoj613/zarr-ml that referenced this pull request Nov 6, 2024
@zoj613
Add ZipStore storage backend.
8f3ad93 
This commit adds a ZipStore storage backend as described in the
specification zarr-developers/zarr-specs#311 .
Note that the implementation loads the entire zip archive into memory so
care must be taken to ensure the zip archive is not too big to fit into
the machine's memory. To use a ZipStore impelementation that does not
load the archive into memory see `examples/zipstore.ml`.
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@jhamman @joshmoore @zoj613 @DennisHeimbigner