[Monetdb-developers] Testing update performance of MonetDB
lukaskircher1 at googlemail.com
Wed Aug 25 21:25:55 CEST 2010
I'm currently writing my bachelor's thesis at the university of
Konstanz about extending BaseX  with XQuery Update. I wanted to
compare evaluation times between MonetDB and BaseX, as they have
comparable table layouts, but am facing several problems.
So far I read your manual that suggests to use functions to support
caching, as well as limiting inserts to a single position in a
document. Some papers provided insight too [2,3], still there are
questions (hopefully I didn't miss anything on your mailing lists and
I hit the right one):
1. General storage:
In which way is free space reserved, if an updatable document via
fn:add-doc(u, x, y, freeSpace) is added? Let's assume freeSpace = 10%.
Does this mean that free space (equal to 10% of our document size) is
allocated between all used pages on disk? Spoken clearly, one tenth of
free space on every page? But this would be in conflict with the
suggestion to limit inserts to a single position in a document...
What happens during the 'Print'...ing part when I use the '-t' flag
for timings? Query time is amazingly fast, yet I experience unusually
long printing times - even for a small test document. Increasing the
free space variable (see question 1) results in even longer printing
times, which is on one side perfectly understandable as more pages on
disk are used (right?)...
3. Yet, on the other side empty space on disk should not be accessed?
I expect there to be a balance between query performance and free
space? Is there a rule of thumb I can apply to get the most out of
MonetDB (regarding specific queries of course)?
4. Are there any general advises for testing update performance of
I could gain some knowledge from a previous post on the developers
list - yet I feel it's not enough to explain the results of my (yet
immature) tests and to do your system justice ...
Thanks for your help! Looking forward to your answer...
 Updating the Pre/Post Plane in MonetDB/XQuery
 MonetDB/XQuery: A Fast XQuery Processor Powered by a Relational
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