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From Igor Rudyak <irud...@gmail.com>
Subject Re: Cassandra store questions
Date Fri, 07 Oct 2016 06:00:52 GMT
Hi Val,

1) If you'll call loadCache(null) it will do nothing. You need to provide
at least one CQL query.

2) It depends. If you'll provide more than one CQL query, it will use
separate thread for each of the queries (max number of threads limited to
the number of CPU cores). But for each provided CQL query it will use only
one thread to load all the data returned by the query. Also it will run the
same CQL query from ALL Ignite nodes to load the same data, which is bad.
That's because loadCache method will be executed on each Ignite node. As
you see, it's not very efficient way to load data from Cassandra just by
specifying CQL query. The ticket I created, is all about how to load data
from one table (or from multiple tables as well) in parallel by
partitioning it. Such a way each Ignite node will be responsible to load
data from the specific partition range of Cassandra table, which is much
more efficient. To support such kind of cache warm-up you should design
your Cassandra table specific way - there should be some mapping from
Ignite partition to the set of Cassandra partitions. Yes I have plans to
implement this.

Igor Rudyak

On Thu, Oct 6, 2016 at 10:19 AM, Valentin Kulichenko <
valentin.kulichenko@gmail.com> wrote:

> Hi Igor,
> I've got couple of quick questions about the Cassandra store.
>    1. In [1] you suggested to provide an explicit query as a parameter
>    for loadCache() method, because otherwise user was always getting empty
>    result. Is this a requirement to provide the query? What if I just call
>    loadCache(null)?
>    2. There is a ticket [2] about parallel load in Cassandra store. Does
>    it mean that currently it loads only in a single threaded fashion? If so,
>    do you have any plans to implement this improvement?
> [1] http://apache-ignite-users.70518.x6.nabble.com/
> Cannot-query-on-a-cache-using-Cassandra-as-a-persistent-store-td7870.html
> [2] https://gridgain.freshdesk.com/helpdesk/tickets/2180
> Thanks,
> Val

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