Zarr DirectoryStore: getsize is wrong

[Kriechi]

https://github.com/zarr-developers/zarr/blob/3c8e9291e96e090e20caf6950da69a3cc180652f/zarr/storage.py#L864-L871

This code does not account for subfolders created by this example:

store = zarr.TempStore(dir='/tmpfs')
for name, values in data.items():
    zarr.array(values, store=store, path=name, compressor=compressor, filters=filter)
total_size = store.getsize()

total_size is 26, (24+2 for .zattrs and .zgroup), which is wrong. Subfolders are not accounted for.

My TempStore has the following structure:

.zattrs
.group
name1/
  1
  2
  3
name2/
  1
  2
  3

The file sizes of name1 and name2 are unaccounted for.

Tested with Zarr 2.2.0.

[alimanfoo]

Thanks Thomas, currently on leave but will follow up next week.

On Wed, 4 Apr 2018, 15:35 Thomas Kriechbaumer, [email protected] wrote:

https://github.com/zarr-developers/zarr/blob/3c8e9291e96e090e20caf6950da69a3cc180652f/zarr/storage.py#L864-L871

This code does not account for subfolders created by this example:

store = zarr.TempStore(dir='/tmpfs')for name, values in data.items(): zarr.array(values, store=store, path=name, compressor=compressor, filters=filter) total_size = store.getsize()

total_size is 26, (24+2 for .zattrs and .zgroup), which is wrong. Subfolders are not accounted for.

My TempStore has the following structure:

.zattrs .group name1/ 1 2 3 name2/ 1 2 3

The file sizes of name1 and name2 are unaccounted for.

Tested with Zarr 2.2.0.

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[alimanfoo]

Just to say the getsize() method was originally added to provide information about stored size of a single array, and so recursing into subdirectories was not needed. However I think it would be better in general if it did report recursive size. I don't have time to work on this right now but a PR would be welcome.

Also if this was changed to recursive size in DirectoryStore then might want to also review implementation in NestedDirectoryStore and ZipStore classes.

[jakirkham]

So I guess NestedDirectoryStore would technically be wrong too or does that already recurse when determining array size.

[alimanfoo]

Yes NestedDirectoryStore is wrong, only counts immediate children of a directory (actually doesn't override getsize() so uses implementation from parent class DirectoryStore).

[jakirkham]

It would be pretty simple to change this to os.walk.

If we want to get fancier, we use scandir, which includes the size while walking the tree. There's a backport package for Python 2 as well.

ref: https://stackoverflow.com/a/1392549

[jakirkham]

PR ( https://github.com/zarr-developers/zarr/pull/362 ) should fix this. Just used os.walk for simplicity given we need to go through the directory recursively and scandir behaves a bit more like listdir, which would complicate this a bit.

[jakirkham]

When looking into this further, it seems that getsize's behavior is currently expected to ignore nested children. This is tested here (note this should be 15 instead of 6 if recursion is used) as well as on the following lines. This test is run for all stores (e.g. DictStore also has this behavior). While I agree it probably should change to be recursive, that's a behavior change. So it would be good to make sure we are not missing something before changing this.

[jakirkham]

@alimanfoo, do you have any thoughts on the comment above? Basically the current behavior seems intentional (as it is tested) so am trying to understand how we should proceed here.

[alimanfoo]

Sorry for slow follow up. FWIW I think it would be reasonable to change the behaviour and make it recursive. Should not affect results for reporting stored size of an array in a DirectoryStore, as there shouldn't be any sub-directories there anyway. (E.g., I often call .info on an array to see how big it is on disk.) I'm happy for the tests to be modified.

[jakirkham]

Sorry I missed your comment, @alimanfoo. Thanks for the clarification. Happy to break the current tests as well. Just wanted to make sure there wasn't something I was missing. Will try to update PR ( https://github.com/zarr-developers/zarr/pull/362 ) when I have a chance.

[hmaarrfk]

Is the only way to get the current estimated size by parsing the returned value of info_items in our own dictionary then indexing No. bytes stored?

[aliaksei-chareshneu]

Dear all,

Are there any updates on this functionality (getting size of subfolders and arrays recursively)?

Thank you.