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https://issues.apache.org/jira/browse/CASSANDRA-6870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13941899#comment-13941899
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Edward Capriolo commented on CASSANDRA-6870:
--------------------------------------------
{quote}
this should support normal CL conventions. So if I want to trim without paxos
because I'm confident that there are no races, I shouldn't have to pay that
extra latency cost. I think this means we open up CL.SERIAL for normal UPDATE
(without IF) when UDF are being invoked against data from an existing row.
{quote}
I was wondering if it made sense to support transform and transform_atomic for
this case. IE the default transform does not have to happen in paxos at all.
{quote}
sometimes a single output column is not enough. how do we support more? We
could use (c1, c2) = f(c3, c4) syntax similar to what we introduced for
composite partition keys. Or we could add "out" parameters which is what most
SQL UDF implementations do. NB: I am fine with postponing implementation of
this to another ticket, but I do think we should settle on the syntax ahead of
time so that we don't accidentally make extending it harder than necessary.
{quote}
In hive UDF returns a single value. This is a pure definition of function.
There is a different interface UDTF that returns multiple columns or even rows.
It looks like this:
{code}
select parsurl(url, 'host', 'port') as a,b
{code}
I would suggest to differentiate a UDF which works like a mathamatical
function,from a UDTF. Trying to make them one uber-interface would probably
make said interface hard to implement.
> Transform operation
> -------------------
>
> Key: CASSANDRA-6870
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6870
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Edward Capriolo
> Assignee: Edward Capriolo
> Priority: Minor
>
> Compare and swap uses paxos to only update a value only if some criteria is
> met. If I understand correctly we should be able to use this feature to
> provide a wider variety of server side operations.
> For example inside a paxos transaction performing a slice and then using a
> function to manipulate the slice. You could accomplish features like append
> and increment this way without user needing to know the current value.
> I took a stab at doing this. I **think** I did it correctly. Comments welcome.
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