fsspec / fsspec/kerchunk

Time to list a big reference set

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#241 2 comments 0 reactions 0 assignees View on GitHub

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Dominant language
Python
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Description

When xarray opens a zarr dataset, the first thing it does is ls("") on the root, to find out the "directories" contained, each of which will be an array. If each array has many chunks, this takes a long time, since we consider every single key in building the directory structure, with string processing on each.

Suggestion: to store the set of directories (or a tree, if deep) in the reference set, to avoid having to do this every time. This would require changing the spec and updating referenceFS.

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Research direction

Start with the current reference-set specification and the referenceFS implementation, then trace the root ls("") path that builds the directory structure. Determine how directory or tree metadata would fit the specification and implementation. Done means the specification and referenceFS agree on the stored metadata and root listing no longer processes every key individually.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
data-engineering
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
30/100

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