Scratch deltas should be fetched when current rev is partial #2004
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Also flatpak/flatpak#3413. |
dbnicholson
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Feb 12, 2020
In e7305bb a heuristic was added that if a scratch delta exists but you already have a commit on that ref that an object pull should be preferred. The idea is that if you already have something on the ref, then it's likely that an object pull require less data to be fetched than pulling the entire new commit. However, if the existing commit is partial then it might be better to fetch the scratch delta. In particular, if the existing commit is partial because a metadata only pull has been done, then definitely it would be better to pull the scratch delta. It would be best to figure out the size of the needed objects vs the size of the scratch delta, but that information is not typically available. Prefer a scratch delta in this case. Closes: ostreedev#2004
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I dunno if this is right. The way the current flatpak code works the ref will always be seen as pointing to the new, partial object. However, before the pull of the commit it may very well be the case that the ref pointed to a complete commit and we have a lot of data, so using a from-scratch delta is a bad idea. |
dbnicholson
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Feb 13, 2020
In e7305bb a heuristic was added that if a scratch delta exists but you already have a commit on that ref that an object pull should be preferred. The idea is that if you already have something on the ref, then it's likely that an object pull require less data to be fetched than pulling the entire new commit. However, this doesn't take into account the commit state. If the existing commit is partial, then it might be better to fetch the scratch delta. On the other hand, if the existing commit is partial only because a metadata only pull has been done, then the parent commit might be normal and then you'd want to prefer an object pull again. Instead of considering just the HEAD local commit, walk the parents and check if any of them are normal commits. Only then use an object pull. Closes: ostreedev#2004
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In e7305bb a heuristic was added that if a scratch delta exists but you already have a commit on that ref that an object pull should be preferred. The idea is that if you already have something on the ref, then it's likely that an object pull require less data to be fetched than pulling the entire new commit.
However, if the existing commit is partial then it might be better to fetch the scratch delta. In particular, if the existing commit is partial because a metadata only pull has been done, then definitely it would be better to pull the scratch delta.
See flatpak/flatpak#3412.
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