Thank you everyone for answering my questions.
Here is the way I understand it. The first time a view is run it
creates a key-values list from all documents. Future calls to the
view, update the key-value list with changed documents [added,
deleted, updated].
If a startkey, endkey or key is used, only those keys that match in
the list are returned.
If I use a different startkey, endkey or key, the key-value list is
not rebuilt, it uses the keys from the first view.
Did I get it right?
Sorry about being obtuse. I have a project that can have over 10
million documents and I need to understand how they can be indexed.
Thank you,
Anthony
On Apr 26, 2008, at 2:11 PM, Jan Lehnardt wrote:
Heya Anthony,
On Apr 26, 2008, at 20:50, Anthony Mills wrote:
Maybe I missing something. When you create a view, does it create
indexes for attributes in the database? When you add new
documents, do they automatically create the index for the
attributes for the view?
A view index only has a single index which is what you send in as
the first argument in the map() function. Nothing else is going on
automatically.
Also, can I call my view with soemthing like ?
startkey=['20080403t000000', 1234]&endkey=['20080405t235959', 1234]
to
function(doc){
if(doc.type == "hello"){
map([doc.date, doc.number], doc);
}
}
Then, through the magic of couchdb, I'll only get back those
documents between the April 3rd and 5th whose attribute number=1234?
Nope, you'd need a [doc.number, doc.date] index for that. It is
rather straightforward than magical. The map() function just creates
a key-value list that is sorted by key and you can query only ranges
within the key-space.
Will couchdb only search through records that match the key? or
will it need to go through all documents every time I call the view?
To build the view index CouchDB will go through all documents. But
only once. For documents that change, get deleted or added, CouchDB
incrementally updates the index. Also, view indexes are build when
you query the view, not when you add documents.
To get nerdy, I want my views to find records in O(log n) not O(n).
You get your results in O(1) ;-) (after the first query to each view).
In relational terms, think of a view as an index on a column without
the write penalty. So have as much as you might need.
I hope that helps, feel free to send more questions :)
Cheers
Jan
--
Thanks,
Anthony
On Apr 26, 2008, at 1:02 AM, Chris Anderson wrote:
Anthony,
http://wiki.apache.org/couchdb/ViewCollation is the way to
accomplish
tasks like that.
Christopher Lenz has a write-up of how to use view collation to sort
views, achieving comments grouped by parent blog post.
http://www.cmlenz.net/archives/2007/10/couchdb-joins
In your case you could index a view with date and type, like this
[type, date]
and then if you had say 5 types you'd do 5 GET queries against the
database, each one fetching only the documents for that day.
View collation is one of my favorite things about CouchDB. I'm
excited
about reduce, because from what I understand, you could use it to
lower this to 1 GET, if that's important to you.
enjoy,
Chris
On Fri, Apr 25, 2008 at 9:34 PM, Anthony Mills <[EMAIL PROTECTED]
> wrote:
I read most of the documentation, wiki and blogs, but I still do
not see how
to accomplish a certain scenario. Hopefully I can describe it
adiquitely.
Lets say I have 1,000,000 documents [all of the same "type"] with
a date
attribute. Lets say I want to pick a subset of those documents.
How can I
pick those documents of one type that fall on one day? Will I
need to get
all 1,000,000 documents? What if I want all documents of one
type on one
day that match another attribute?
I pretty sure this is what map/reduce will help with, but is
there a way to
do this now? Can you use more documents to build date relations?
Also, can you pass more variables than just key to
