Hi Venkat, You can find those settings in our docs: http://docs.basho.com/riak/1.4.9/ops/advanced/backends/bitcask/#Configuring-Bitcask (search for “Fold Keys Threshold”).
In Bitcask when we do range operations like “List Keys” or other operations that require us to fold over all the data, we take a snapshot of the “Keydir” to get a consistent read. The Keydir is the hash table that holds the `key-> latest object` mapping. When we do this snapshot, we also start a delta of any changes since the snapshot. We use the two “Fold Keys Threshold” options `max_fold_age` and `max_fold_puts` only when Bitcask is processing one fold operation, and gets a request for a second one. These two options let the user choose whether to reuse the snapshot, or to block and get a new snapshot before starting the second fold. This lets you tradeoff between a potential performance boost and consistency. By default we have Bitcask side toward consistency; it will get a new snapshot, by setting `max_fold_puts` to `0`. If any new puts come in, we must grab a new snapshot before folding again. - Increasing `max_fold_puts` to `n` will let Bitcask reuse the snapshot if there are fewer than `n` changes in the delta. - Increasing `max_fold_age` to `s` will let Bitcask reuse the snapshot if the snapshot is younger than `s` microseconds. Setting either of these to positive values can let folds ignore recent changes, so you can run into stale data. Because of that, we recommend that you don’t change them. I hope this helps. Thanks, Alex On May 13, 2014, at 3:02 PM, Venkatachalam Subramanian <venkatsubb...@gmail.com> wrote: > Hi All, > > It was very helpful to get my first few questions about Riak/Bitcacsk > answered pretty quickly. > > I just have a another question on the same lines, > > I ran across the 'fold keys threshold' option in riak/bitcask. > I could not find enough information about the 'fold keys' option to > understand it completely. > > Could someone tell me what 'fold keys' option is? what does it do? when could > we use it? > Does it help when you want to get the list of all keys available? > > I greatly appreciate your help. > Thank You. > > -- > Regards, > Venkat Subramanian > > > _______________________________________________ > riak-users mailing list > riak-users@lists.basho.com > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
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