Hi Constantin, this is definitely the right list :) Have you seen the work on the new “Mango” query processor? The README on the repo is probably the best resource:
https://github.com/apache/couchdb-mango If the elements of your key array are pulled directly from fields of the document then it would be possible to execute a keymask using a _find invocation. The Mango query processor will use the index you create and then do an Erlang-based filter of the remaining rows to satisfy the exact query. There are a few limitations to Mango at the moment: - Mango wants its own indexes, it doesn’t know how to incorporate user-defined MR views - The indexes do not allow for any custom processing of the document fields that are included - Reduce functions are not supported I’d be curious to hear if that would address your use case. Cheers, Adam > On Mar 6, 2016, at 3:42 AM, Constantin Teodorescu <braila...@gmail.com> wrote: > > Hello all, a quick use case for a new "keymask" option in views: > > We have a view with keys as array like [ k1 , k2 , k3, k4] > we're using, most of the time, reduces and data processing using: > "startkey": [ k1 , ""], > "endkey": [ k1 , "\ufff0"] > > Sometimes I feeld that it would be just fantastic to have a filtering > option on keys like: > "startkey": [ k1 , ""], > "endkey": [ k1 , "\ufff0"], > "keymask": [ null, null, "desired k3 value" , null], > "reduce": false, > > that would filter anything between the startkey and endkey WHERE k3 = > "desired k3 value" > > Sometimes, there is a need for more than a unique design of the view tree > keys, to access data grouped in another way. > Of course, we can acomplish that: > - defining a new map/reduce function [k1,k3,k2,k4] (waste of disk space, > time consuming) > - using a _list function that will do the trick (slower, that's what I am > doing now) > > But introducing the "keymask" option in view, filtering rows right at the > core of CouchDB, in Erlang, without expensive traffic to the query server, > would speed things a lot. And I'm thinking that it wouldn't be so hard to > do it. I hope ... ;-) > > Of course, "keymask" will be usable ONLY when "reduce":false , otherwise > reduce values will be garbage! > > Constantin Teodorescu > A long time watcher, fan and user of CouchDB, even in the nation-wide > animal identification system in Romania and farmers subsidies. > Now working on a "killer app", a new and astonishing small business > accounting and information management system in CouchDB! > P.S. I'm not sure that this is the right mailing list to address this > proposal but ... maybe it's interesting for anyone!
