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From Yakov Zhdanov <yzhda...@apache.org>
Subject Re: Closure method on a Cache Query
Date Fri, 12 Jun 2015 08:44:43 GMT
I am crossposting this to dev list as well.

So, is there a way to introduce custom aggregate function? I assume no.

But even if we have such ability, writing and plugging such custom function
seem to  be much harder to do than direct reducer/transformer from java
code. However, this is not very common usecase in SQL, I think.

I think it would be very nice to support custom aggregate functions. As far
as java-reducers - this is not very intuitive and I would skip adding them
back if custom aggregate is possible.

Sergi, Alex, can you please share your opinions?


2015-06-09 22:21 GMT+03:00 Dmitriy Setrakyan <dsetrakyan@apache.org>:

> Also, if you need to return only a portion of the object (just a few
> fields), you can use SqlFieldsQuery and select only specific fields:
> select a, b, c from Person...
> D.
> On Tue, Jun 9, 2015 at 1:20 PM, fluffy <fhafner@gmail.com> wrote:
>> Using GridGain, I used to be able to associate a GridClosure method with a
>> GridCacheQuery. You could simply pass this Closure method into the
>> GridCacheQuery.execute() function and it would perform a function on each
>> cache element that matched the SQL query.
>> This basically consolidated a number of tasks:
>> - Instead of receiving entire objects from a query, a much smaller result
>> value was sent back to the node that initiated the query
>> - Allowed for the specification of some functionality within each Cache
>> Element rather than being a fairly dull data store
>> - Allowed for distributed processing of Cache Element information on the
>> node that each valid element existed before being aggregated/merged on the
>> calling node
>> I do not see this functionality as having been ported to the Ignite
>> release.
>> At least not directly. Is there a way to do this in the current Ignite
>> version?
>> I was looking at either a ScanQuery or using the AffinityRun methods, but
>> the later don't seem to allow me to perform an SQL query first to limit
>> the
>> Cache Elements....
>> --
>> View this message in context:
>> http://apache-ignite-users.70518.x6.nabble.com/Closure-method-on-a-Cache-Query-tp456.html
>> Sent from the Apache Ignite Users mailing list archive at Nabble.com.

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