Re: ORMs comparisons/complaints.
On 12/31/2013 9:30 AM, Marcel M?ller wrote:
On 30.12.13 22.03, Arved Sandstrom wrote:
There is one advantage. Adding attributes to the data model is quite
simple with an ORM. No need to do redundant changes at many locations.
But any document DB will provide this as well without the need for SQL
and an ORM.
By regarding your data as being document-oriented you already made a
fundamental decision that your data is semi-structured or
non-structured.
Well, an XML is a document too, and most of the time it is well structured.
It can be but does not need to be.
If there is a schema defining the format and data get validated against
it then it is well structured.
That also carry some of the same restrictions as relational databases
even though XML schemas allow for much more flexible structures
than database tables.
If there are no schema or validation then there are no structure
enforced.
I do not really have experience with NoSQL databases. But I used non
relational data models and in memory computing now for about 6 years in
different projects. None of the projects failed, all are still live.
Also we did not really save resources because of the decisions made. But
from the code maintenance and from the performance point of view it was
successful. Some change requests to the first of these projects were
implemented by an apprentice in half an hour. This would have taken a
few days by a qualified programmer, if we had chosen a relational data
model.
In the last project - a larger one - we have significant performance
benefits. There is an adjacent third party application with a very
similar data model from the customers point of view. (They are better
with respect to inheritance, we are better with respect to deep
structures but both can deal with polymorphism, table properties an so on.)
They ended up with solution d). We use XML documents. Measurements show
about three orders of magnitude performance difference, measured in time
per object access. We have two CPU cores with <30% load if users make
traffic. They have 16 CPU at 80-100% load if users make traffic. The
number of objects and attributes is comparable. In fact the data is
partially synchronized by interfaces. Both are Web applications. The
number of users is comparable.
OK, they have chosen PHP (used in an object oriented way), we have .NET
3.5. But this will not explain all the 3 orders of magnitude. Their
system creates heavy load on the large attribute values table.
There are plenty of cases where relational databases are not the best
solution.
Google, Facebook, Yahoo etc. did not go NoSQL just for fun.
But I would still consider a relational database to be the default
for persistence - what you use unless you have specific reasons
not to.
Arne