On Aug 3, 2010, at 7:31 PM, Steven Prentice <[email protected]>
wrote:
> Hey Couchinators!
>
> My friend and I are trying to test the impact that views have on the size of
> the database and have a few questions...
>
> 1. if the value of a view is set to 'doc' does that mean that the leaves of
> the view B-Tree are now documents or are they simply pointers to the
> document leaves in the database B-Tree?
> i.e would the summed memory of all of the values in the view be equal to the
> size of the database (ignoreing revisions)?
Whatever you emit as a value is stored in the btree. So if you emit an entire
document it is stored completely in that view. A way to avoid this is to use
the include_docs=true parameter but it has some read performance trade offs
because it's a lookup per view row. The best idea is to only emit what's
actually needed.
> 2. also we would like to know if the database size that is displayed in
> futon includes the size of the views?
Unless I missed that commit, no, db size is the size of just the .couch file.
> 3. Oh also, Revisions...is a revision an entire document or does a revision
> only track changes in a document?
Neither. A revision is just the string-id pair (More precisely it's a node in
the revision tree, but it still has zero info on actual document content).
That's all that will remain on disk after a compaction. Because we're tail
append the previous entire documents remain on disk until compaction. To
illustrate, we've had discussions on removing access to old revisions and
renaming revision to something else that doesn't make people think they'll
always have access to old versions of a document.
> Cheers
> Steve + Adam
HTH,
Paul Davis
