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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-7809) UDF cleanups (#7395 follow-up)
Date Thu, 21 Aug 2014 13:54:11 GMT
Sylvain Lebresne created CASSANDRA-7809:
-------------------------------------------

             Summary: UDF cleanups (#7395 follow-up)
                 Key: CASSANDRA-7809
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7809
             Project: Cassandra
          Issue Type: Bug
            Reporter: Sylvain Lebresne
             Fix For: 3.0


The current code for UDF is largely not reusing the pre-existing mechanics/code for native/hardcoded
functions. I don't see a good reason for that but I do see downsides: it's more code to maintain
and makes it much easier to have inconsitent behavior between hard-coded and user-defined
function. More concretely, {{UDFRegistery/UDFFunctionOverloads}} fundamentally do the same
thing than {{Functions}}, we should just merge both. I'm also not sure there is a need for
both {{UFMetadata}} and {{UDFunction}} since {{UFMetadata}} really only store infos on a given
function (contrarly to what the javadoc pretends).  I suggest we consolidate all this to cleanup
the code, but also as a way to fix 2 problems that the UDF code has but that the existing
code for "native" functions don't:
* if there is multiple overloads of a function, the UDF code picks the first version whose
argument types are compatible with the concrete arguments provided. This is broken for bind
markers: we don't know the type of markers and so the first function match may not at all
be what the user want. The only sensible choice is to detect that type of ambiguity and reject
the query, asking the user to explicitly type-cast their bind marker (which is what the code
for hard-coded function does).
* the UDF code builds a function signature using the CQL type names of the arguments and use
that to distinguish multiple overrides in the schema. This means in particular that {{f(v
text)}} and {{f(v varchar)}} are considered distinct, which is wrong since CQL considers {{varchar}}
as a simple alias of {{text}}. And in fact, the function resolution does consider them aliases
leading to seemingly broken behavior.

There is a few other small problems that I'm proposing to fix while doing this cleanup:
* Function creation only use the function name when checking if the function exists, which
is not enough since we allow multiple over-loadings. You can bypass the check by using "OR
REPLACE" but that's obviously broken.
* {{IF NOT EXISTS}} for function creation is broken.
* The code allows to replace a function (with {{OR REPLACE}}) by a new function with an incompatible
return type. Imo that's dodgy and we should refuse it (users can still drop and re-create
the method if they really want).




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