Get size of acid-state?

[CSchank]

I am wondering if there is a good / reliable way to find out how much space a given acid-state instance is taking up? Would finding the size of the latest checkpoint be a good measure of the memory taken by that instance? If there isn't a good way to do this currently, perhaps it could be added to the library? We'd like to be able to easily monitor how big our databases are getting.

Thanks for your help.

Best regards,
Chris

[lemmih]

You could use Data.Compact: http://hackage.haskell.org/package/compact-0.1.0.1/docs/Data-Compact.html

compactSize <=< compactWithSharing :: a -> IO Word

[adamgundry]

That's a nice trick, albeit potentially expensive.

The size of the latest checkpoint on disk is probably going to be roughly proportional to the heap size in most cases, although this will depend a bit on the efficiency of your in-memory vs binary representations and on how much sharing you have.

Another option in the wild is to manually define an operation to calculate the heap size of your data (e.g. hackage-server does this via the MemSize typeclass). This has the downsides that it is a bit of manual work in which you have to get the calculations right, of course, and it doesn't take account of sharing.

[CSchank]

Thanks for the suggestions. The first one doesn't work with our data. We could do the second thing but the effort might not be worth it. We also tried ghc-datasize (http://hackage.haskell.org/package/ghc-datasize) but that doesn't seem to have been updated to work with newer ghc versions.

Thanks anyway for the suggestions.

Any other suggestions people have would be welcomed.