Re: ORMs comparisons/complaints.
On 1/4/2014 12:15 AM, Arved Sandstrom wrote:
On 01/03/2014 10:56 PM, Arne Vajh?j wrote:
[ SNIP ]
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.
Quite a few important companies (so probably many more minor companies)
played with NoSQL for a bit, and then have backed off in various
degrees. Nobody went for NoSQL just for fun...most went for it because
they were sucked in by hype or misguided opinion. I'd estimate that the
majority of people have returned to RDBMSs. The fact that a number of
large companies have systems that are not relational is because you
can't throw away a few tens or hundreds of millions of $$ in a few
months or years.
NoSQL is based on relaxing ACID, particularly consistency. You do that
by cheating your end users through increasing UI speed, while at the
same time decreasing the validity of your data.
There is a lot more to it than that.
NoSQL is really many different things.
There are some large distributed database systems. There are some
which I would call modern replacements for traditional ISAM files.
Some are AP. Some are CP. CouchDB and Neo4J are ACID.
The big internet companies did not go to NoSQL due to the hype - as
the hype was created by them going to NoSQL and they are not staying
with NoSQL to avoid a large write off. They are went to and are
staying with NoSQL, because the relational databases can not do
the job. Relational databases and PB just does not work performance
and cost wise.
I am sure that there is a large portion of smaller companies that went
NoSQL (typical something "ISAM like") that did so due to the hype. And
I am sure that some of them regretted that they did so.
But persistence is not a one size fit all. Different requirements can
lead to different solutions.
C is critical in many contexts (like money transactions). But there are
other contexts where it does not matter (does it matter that Facebook
users in Mexico sees an update 5 minutes later than the Facebook users
in Finland? No!).
There are quite a few of those C & ACID relational databases where
for performance reasons the web apps in front actually cache and
use data for N seconds even though the data may have been updated. In
that case they are paying for C & ACID for no reason.
All that said then I still consider relational the default choice.
Especially for small startups. One get a lot of functionality and
features that may be useful. If later a need for something with
less functionality & features but higher performance for config
shows up, then it can be valid to change.
Or to put it another way: to me choosing NoSQL is an optimization
and general rules about premature optimization applies.
Arne