It does seem like a place where user defined funcs could work. (Here are some documents, give us a string to index on). Now whether the complexity of supporting user defined functions is worth the effort..
John =:-> On Jul 17, 2012 5:52 AM, "Eric Casteleijn" <[email protected]> wrote: > > Hi Jason, > > I thought it might be instructive (for me ;) to try and see to what extent > those views could be implemented with the current state of the art of u1db. > Note that I probably will get stuck somewhere, as u1db > indexes are much much simpler than couchdb views. > > Each file in Dmedia has a corresponding doc in CouchDB. This is an >> example doc with the essential schema that drives all the automation >> behaviors (the "make file management go away" aspect of Dmedia): >> >> { >> "_id": "**WEFB4GYQBWOEGCUA5AZEXOKWHCB4IU**SYZ2TGJBJUPFWTWCNL", >> "type": "dmedia/file", >> "time": 1338560151.467609, >> "atime": 1342088785, >> "bytes": 26566829, >> "origin": "user", >> "stored": { >> "3KX6WX6YAUQIQ7M2Y3BMPSAI": { >> "copies": 1, >> "mtime": 1338564292, >> "verified": 1338571742 >> }, >> "PSRJGX2O2N77XLBEBI2TNDNU": { >> "copies": 1, >> "mtime": 1338560150, >> "verified": 1338564292 >> }, >> "YE4SYZAVTFEBDI2JZQBUTYQY": { >> "copies": 1, >> "mtime": 1338560150 >> } >> } >> } >> >> This particular file is stored in 3 different "stores" (let's say hard >> drives, but a store could also be something like UbuntuOne or S3). >> Each of these stores has a durability confidence of 1 copy, and the >> total durability for this file is 3 copies. And the copy in the last >> store hasn't yet been verified (full content-hash verification). >> >> The "stored" dictionary was the hardest thing to get right. Hopefully >> And here's the 4 view functions, respectively, that drive these 4 tasks: >> >> file_stored = """ >> function(doc) { >> if (doc.type == 'dmedia/file') { >> var key; >> for (key in doc.stored) { >> emit(key, null); >> } >> } >> } >> """ >> > > This one's not currently supported but could easily be if a 'keys' index > mapping were to be added, and then the index would be: > > doc.type, keys(doc.stored) > > > file_verified = """ >> function(doc) { >> if (doc.type == 'dmedia/file') { >> var key; >> for (key in doc.stored) { >> emit([key, doc.stored[key].verified], null); >> } >> } >> } >> """ >> > > this one is harder, as we don't have a way to peek into variable parts of > the document, and it's not immediately obvious to me how that could be > added without adding a great deal of complexity, so this might just be a > use case that u1db is too simple for. (Restructuring the document to > contain a list of the keys somewhere would work, but that's assuming you > can and want to do that.) > > file_fragile = """ >> function(doc) { >> if (doc.type == 'dmedia/file' && doc.origin == 'user') { >> var copies = 0; >> var key; >> for (key in doc.stored) { >> copies += doc.stored[key].copies; >> } >> if (copies < 3) { >> emit(copies, null); >> } >> } >> } >> """ >> > > Same for this one. We intentionally didn't support any kind of real logic > in the views, to reduce complexity, both for view authors, and for the > indexing engine. > > file_reclaimable = """ >> function(doc) { >> if (doc.type == 'dmedia/file' && doc.origin == 'user') { >> var copies = 0; >> var key; >> for (key in doc.stored) { >> copies += doc.stored[key].copies; >> } >> if (copies >= 3) { >> for (key in doc.stored) { >> if (copies - doc.stored[key].copies >= 3) { >> emit([key, doc.atime], null); >> } >> } >> } >> } >> } >> """ >> > > And same for this one. > > -- > eric casteleijn > https://launchpad.net/~**thisfred <https://launchpad.net/~thisfred> > > > > > -- > Mailing list: > https://launchpad.net/~u1db-**discuss<https://launchpad.net/~u1db-discuss> > Post to : > [email protected].**net<[email protected]> > Unsubscribe : > https://launchpad.net/~u1db-**discuss<https://launchpad.net/~u1db-discuss> > More help : > https://help.launchpad.net/**ListHelp<https://help.launchpad.net/ListHelp> >
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