I don't think so, but check his script on github. Here's a link to the lines. http://github.com/konrad/couchdb-benchmarking/blob/master/couchdb-benchmarking.rb#L84
On Mon, May 31, 2010 at 17:39, Nicholas Orr <[email protected]> wrote: > Ahh yes, I see that now... > > Is that what the grey faint line on the end of those graphs represent? > I actually didn't notice that the first time, just thought the black > line going up was it... > > On Tue, Jun 1, 2010 at 10:13 AM, Randall Leeds <[email protected]> > wrote: >> If you look at the script the compaction is only performed at the end >> and not on each iteration. >> >> On Mon, May 31, 2010 at 16:58, Nicholas Orr <[email protected]> wrote: >>> This all makes sense except the OP says a compaction step is being >>> performed. >>> A compaction is essentially a copy/paste/delete/rename operation, so the on >>> disk size should be fairly constant as the data copied is just the info >>> required isn't it? >>> >>> Nick >>> >>> On Tue, Jun 1, 2010 at 9:39 AM, Randall Leeds >>> <[email protected]>wrote: >>> >>>> Hi Konrad, >>>> >>>> I'll take a stab at this and if I'm wrong hopefully someone will correct >>>> me. >>>> >>>> The on disk BTree is written in an append only fashion rather than >>>> modified in place. Append only updates mean that every inner node of >>>> the BTree along the path from the root to the new update has to be >>>> re-written each time. Initially, when there are very few inner nodes, >>>> the amount of disk space used for each new update is relatively >>>> constant. Since the tree has a large fan-out the depth does not change >>>> much at first. In the second graph you are seeing a tree that has a >>>> depth of 1 (just the root) being written over an over again to disk >>>> and the corresponding expected linear growth results. However, when >>>> you have a higher revision limit the old revisions are kept in the >>>> tree and the tree grows taller and fatter with each update. As you >>>> make more updates more inner nodes need to be rewritten for each >>>> update which causes the growth to accelerate. Eventually, you hit the >>>> revision limit and old revisions are discarded, the tree stops getting >>>> any taller or fatter and the number of inner nodes that need to be >>>> changed for each update remains relatively constant (but greater than >>>> in the case of rev_limit=1). I suspect that the first graph becomes >>>> linear above 1000 updates and does not continue to accelerate. >>>> >>>> Cheers, >>>> Randall >>>> >>>> 2010/5/31 Konrad Förstner <[email protected]>: >>>> > Hi, >>>> > >>>> > I have an issue with CouchDB and posted the question on stackoverflow >>>> > [1] but did not get any helpful answer. I would be great if somebody >>>> > could answer this here or a stackoverflow (there I also had a problem >>>> > with the compaction which was just a timing issue as explaint in the >>>> > comment) >>>> > >>>> > I was wondering why my CouchDB database was growing to fast so I wrote >>>> > a little test script [2]. This script changes an attributed of a CouchDB >>>> > document 1200 times and takes the size of the database after each >>>> > change. After performing these 1200 writing steps the database is >>>> > doing a compaction step and the db size is measured again. In the end >>>> > the script plots the databases size against the revision numbers. The >>>> > benchmarking is run twice: >>>> > >>>> > * The first time the default number of document revision (=1000) is used >>>> (_revs_limit). >>>> > >>>> > * The second time the number of document revisions is set to 1. >>>> > >>>> > The first run produces the following plot >>>> > http://www.flickr.com/photos/konradfoerstner/4656011444/ >>>> > >>>> > The second run produces this plot second run >>>> > http://www.flickr.com/photos/konradfoerstner/4656012732/ >>>> > >>>> > For me this is quite an unexpected behavior. In the first run I would >>>> > have expected a linear growth as every change produces a new >>>> > revision. When the 1000 revisions are reached the size value should be >>>> > constant as the older revisions are discarded. >>>> > >>>> > In the second run the first revision should result in certain database >>>> > size that is then keeps during the following writing steps as every >>>> > new revision leads to the deletion of the previous one. >>>> > >>>> > I could understand if there is a little bit of overhead needed to >>>> > manage the changes but this growth behavior seems weird to me. Can >>>> > anybody explain this phenomenon or correct my assumptions that lead to >>>> > the wrong expectations? >>>> > >>>> > Many thanks in advance >>>> > >>>> > Konrad >>>> > >>>> > [1] >>>> http://stackoverflow.com/questions/2921151/why-do-my-couchdb-databases-grow-so-fast >>>> > [2] http://github.com/konrad/couchdb-benchmarking >>>> > >>>> > >>>> > >>>> > >>>> > >>>> > >>>> >>> >> >
