On Jun 13, 2008, at 00:07, Brad Schick wrote:
On 06/12/2008 11:27 AM, Brad Schick wrote:
One thing that I haven't found in the couchdb API that surprises me,
however, it a way to directly add or modify individual fields
within a
document. For example, how would I efficiently update just one
field in
a few thousand large-ish documents?
...
My first thought was that this could be implemented this with
server-side script functions related to views and/or with HTTP
methods
on field URIs.
Follow up questions on this: Does CouchDB internally track and
reference
individual fields? Or is the json for each document basically a blob
to
everything except View code?
Documents are stored into native Erlang types representing each
document. Except for the view server, no-one cares about what
a document look like.
(caveat: I know little about CouchDB internals, so the following is
based on how I assume it might work)
To complement Views, how about a concept of Modifier scripts? These
would work in two separate stages. First, a map stage would build an
index similar to Views. If CouchDB is able to reference individual
fields, the map would emit a key and field names for each document. If
CouchDB is only able to reference documents, the map would emit just a
key for each document. Then there would be a 'modify' stage that was
run
when the modifier's URI was POSTed to. The modify function would
accept
arbitrary JSON from the PUT, key(s), and either individual fields (if
possible) or entire document(s) (if not). I'd assume the modify
function would have to be called either once per key or with blocks of
keys to avoid holding everything in memory at once.
Why not do just post-modify on the client with caching? I don't really
see
the need to add that to the DB server. Note also, that the map output
can optionally be reduced (and rereduced) which allow further
computations.
Would that be practical? Should I start learning Erlang ;)
You should start learning Erlang in any case :)
Cheers
Jan
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