On 31/12/2008, at 11:29 PM, Geir Magnusson Jr. wrote:
What trouble? I think this is *exactly* what should be done - have
CouchDB store documents that are :
{
metadata : { _rev : X, _id : Y, _woogie: Z, .... anything that
needs to be added in the future, like other metadata like last
update date... },
userdata : { .... the document you want to store .... }
}
and then offer APIs that let you :
a) get to this document, for libraries and clients that know they
are talking to Couch and want to manipulate at this level
b) return and accept the userdocument directly, for clients that
just want to consume or produce JSON data, w/o caring about the
internal housekeeping
One of the issues complicating the logic of this discussion is that
the document id is both metadata and, conceptually, a document member.
That's why, although the purest model is to have the userdata as a
member within a Couch document as you suggest, this doesn't look that
appealing:
{
metadata: {
id: ...
rev: ...
...
}
data: {
... the user's document ...
}
}
Furthermore, from a scalability perspective, always having the
metadata when you have the document, isn't a problem - the metadata is
constrained. The reverse situation of always having the data when you
have the metadata, is not constrained because the data is arbitrarily
large. IMO this means that a solution such as this:
{
id: ...
rev: ...
...
data: {
... the user's document ...
}
}
isn't such a good idea compared to this:
{
_metadata: {
id: ...
rev: ...
}
... the user's document ...
}
Unfortunately the reserved token makes the structure non-reflexive
without transformation, and although that's not currently an issue, I
can imagine it complicating certain use-cases. It makes the system
more complicated to reason about.
I'm struggling to objectively evaluate this model and your reflexive
model - given Damien's attitude to this issue, my motivation to do so
is somewhat depressed :/
Antony Blakey
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