Add MaybeTransaction for better writing speed when supported #584
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Atreyagaurav
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| impl Dataset { | ||
| pub fn maybe_start_transaction(&mut self) -> MaybeTransaction<'_> { | ||
| let force = 1; |
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We should add at some point that parameter for force, but if you want this for better performance, you absolutely don't want to enable it.
I think it only works for FileGDB, and it's implemented by making a file system-level copy of the whole dataset, and restoring it on rollback.
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Yeah that won't help with performance, I think if we want transaction for rollback purposes vs want transaction for speed purposes, I think we should have different methods.
The MaybeTransaction doesn't have rollback method at all, that'd help at compile time to let people know they can't rollback. Since it could be working on the database directly without transaction as well.
That's why I was thinking maybe some other name would be better. The current interpretation of MaybeTransaction is it is maybe a transaction or not, hence it has to be committed on drop, and no rollback. To make the Transaction and non transaction database do same thing.
On that note I think we can add the force thing to normal Transaction or add another ForceTransaction that does filesystem copy ourselves when Transaction fails.
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| impl Dataset { | ||
| pub fn maybe_start_transaction(&mut self) -> MaybeTransaction<'_> { |
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It might be reasonable to go with a callback based approach here instead of having that guard object. This should make it much easier to handle errors on committing.
That would give you the following function signature:
fn maybe_transaction<R,E: From<gdal::Error>>(&self, impl Fn(&Dataset) -> Result<R, E>) -> Result<R,E>For the implementation of that pattern see diesels transaction method.
CHANGES.mdif knowledge of this change could be valuable to users.Fixes #582