Comments (2)
Object backends now support get_all, get_by_prefix and iterate functions. Let me know what you think.
from julea.
There's a few usecases this design doesn't support:
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Filtering by range, instead of prefix. E.g. "give me all objects with names lexicographically between sa* to st*"
- This would require a shared ordering definition between backends
- Lexicographic ordering on byte strings breaks down in the presence of multi-byte characters (e.g. unicode object keys)
- If implemented, could replace get_by_prefix
- Backend would only offer get_by_range
- higher-level API maps get_by_prefix(key) onto get_by_range(key, key_with_last_place_incremented)
- This would complicate backends which can't range-query easily
- Probably shouldn't be supported?
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Partial iteration: cancelling an iteration after finding the object the client was searching for
- While the client can just ignore the iterator, the backend can only free the associated resources if the iterator is exhausted
- Solution could be another function to close an iterator
- What if the iterators of get_all and get_by_prefix require different destruction steps?
- One function for each, or is the backend expected to tag its iterator?
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Fulfillment errors during iteration
- There's no way for backend_iterate to signal an error, because FALSE is interpreted to mean "no more elements"
- Probably fine, as there's not really much information in a bool for the caller to react to
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Metadata reporting along with key name
- If the backend is walking its own metadata anyway, it might be uniquely cheap to also offer access to additional metadata during iteration
- If a client wants to filter for e.g. recent modification time, it would have to call backend_status on each of the keys
- Saves one call per key if the metadata is needed by the client
- "Filter for recent modification" is not a fast usecase even with mtime reporting during iteration
I'm not saying they all should be supported, just making sure they are considered.
from julea.
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from julea.