FoundationDB

Question about range clear


(junius) #1

If there are like millions of keys under one prefix, could I simply call clear(Range) for all keys under the prefix? The range simply includes all possible keys under the same prefix. Will it exceed the size limit of FDB? Or I have to make sure all deleted keys in the clear range are within the size limit?

example api: void clear(Range range) under Java.


(Steve Atherton) #2

Yes, you can. The amount of data contained by the cleared range does not count against the write transaction size limit.


(junius) #3

Thanks! This is great!

Assume FDB commits a single range clear request to the logs. Then Storage Node(s) will pull this range clear request, put a delete marker locally, then start scanning and deleting the keys with control (to avoid spikes, which may impact the read). Is this correct?


(A.J. Beamon) #4

Pretty much, yeah. The storage nodes quickly detach the affected keys from the b-tree on a range clear, and then the detached pages are gradually cleaned up by a background cleanup process.