Sylvain Lebresne created CASSANDRA-7813:
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Summary: Decide how to deal with conflict between native and
user-defined functions
Key: CASSANDRA-7813
URL: https://issues.apache.org/jira/browse/CASSANDRA-7813
Project: Cassandra
Issue Type: Improvement
Reporter: Sylvain Lebresne
Fix For: 3.0
We have a bunch of native/hardcoded functions (now(), dateOf(), ...) and in
3.0, user will be able to define new functions. Now, there is a very high
change that we will provide more native functions over-time (to be clear, I'm
not particularly for adding native functions for allthethings just because we
can, but it's clear that we should ultimately provide more than what we have).
Which begs the question: how do we want to deal with the problem of adding a
native function potentially breaking a previously defined user-defined function?
A priori I see the following options (maybe there is more?):
# don't do anything specific, hoping that it won't happen often and consider it
a user problem if it does.
# reserve a big number of names that we're hoping will cover all future need.
# make native function and user-defined function syntactically distinct so it
cannot happen.
I'm not a huge fan of solution 1). Solution 2) is actually what we did for UDT
but I think it's somewhat less practical here: there is so much types that it
makes sense to provide natively and so it wasn't too hard to come up with a
reasonably small list of types name to reserve just in case. This feels a lot
harder for functions to me.
Which leaves solution 3). Since we already have the concept of namespaces for
functions, a simple idea would be to force user function to have namespace. We
could even allow that namespace to be empty as long as we force the namespace
separator (so we'd allow {{bar::foo}} and {{::foo}} for user functions, but
*not* {{foo}} which would be reserved for native function).
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