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From Semyon Boikov <sboi...@gridgain.com>
Subject Re: Retrieving multiple keys with filtering
Date Mon, 04 Sep 2017 14:18:35 GMT
Yes, read can be executed without acquiring entry lock. But you need take
into account that request for cache.get operation can be processed in the
same stripe as cache.invoke.

Semyon

On Mon, Sep 4, 2017 at 6:39 AM, Dmitriy Setrakyan <dsetrakyan@apache.org>
wrote:

> Semyon,
>
> Can you please clarify this. Do we allow concurrent reads while invokeAll
> or invoke is executed?
>
> D.
>
> On Tue, Aug 29, 2017 at 11:59 AM, Andrey Kornev <andrewkornev@hotmail.com>
> wrote:
>
>> Ah, yes! Thank you, Semyon! According to invokeAll() javadocs "No
>> mappings will be returned for EntryProcessors that return a null value for
>> a key." I should read JCache javadocs more carefully next time. :)
>>
>>
>> Still, the processor is invoked while a monitor is held on the cache
>> entry being processed, which is of course unnecessary in a read-only case
>> like the one we're discussing in this thread...
>>
>>
>> I guess I'm stuck with the Compute-based approach for now. :(
>>
>> Thanks!
>> Andrey
>>
>> ------------------------------
>> *From:* Semyon Boikov <sboikov@gridgain.com>
>> *Sent:* Tuesday, August 29, 2017 6:15 AM
>>
>> *To:* user@ignite.apache.org
>> *Subject:* Re: Retrieving multiple keys with filtering
>>
>> Hi,
>>
>> If EntryProcessor returns null then null is not added in the result map.
>> But I agree that using invokeAll() will have a lot of unnecessary overhead.
>> Perhaps we need add new getAll method on API, otherwise best alternative is
>> use custom ComputeJob or affinityCall.
>>
>> Thanks,
>> Semyon
>>
>> On Tue, Aug 29, 2017 at 7:20 AM, Dmitriy Setrakyan <dsetrakyan@apache.org
>> > wrote:
>>
>>> Andrey,
>>>
>>> I am not sure I understand. According to EntryProcessor API [1] you can
>>> chose to return nothing.
>>>
>>> Also, to my knowledge, you can still do parallel reads while executing
>>> the EntryProcessor. Perhaps other community members can elaborate on this.
>>>
>>> [1] https://static.javadoc.io/javax.cache/cache-api/1.0.0/in
>>> dex.html?javax/cache/processor/EntryProcessor.html
>>>
>>> D.
>>>
>>>
>>> On Mon, Aug 28, 2017 at 8:29 PM, Andrey Kornev <andrewkornev@hotmail.com
>>> > wrote:
>>>
>>>> Dmitriy,
>>>>
>>>>
>>>> It's good to be back! 😃 Glad to find Ignite community as vibrant
>>>> and thriving as ever!
>>>>
>>>> Speaking of invokeAll(), even if we ignore for a moment the overhead
>>>> associated with locking/unlocking a cache entry prior to passing it to the
>>>> EntryProcessor as well as the overhead associated with enlisting the
>>>> touched entries in a transaction, the bigger problem with using
>>>> invokeAll() for filtering is that EntryProcessor must return a value. I'm
>>>> not aware of any way to make EntryProcessor drop the entry from the
>>>> response. The only options is to use a null (or false) to indicate a
>>>> filtered out entry. In my specific case, I'll end up sending back a whole
>>>> bunch of nulls in the result map as I expect most of the keys to be
>>>> rejected by the filter.
>>>>
>>>> Overall, invokeAll() is not what one would call *efficient* (the key
>>>> word in my original question) way of filtering.
>>>>
>>>> Thanks!
>>>> Andrey
>>>>
>>>> ------------------------------
>>>> *From:* Dmitriy Setrakyan <dsetrakyan@apache.org>
>>>> *Sent:* Saturday, August 26, 2017 8:37 AM
>>>> *To:* user
>>>>
>>>> *Subject:* Re: Retrieving multiple keys with filtering
>>>>
>>>> Andrey,
>>>>
>>>> Good to hear from you. Long time no talk.
>>>>
>>>> I don't think invokeAll has only update semantics. You can definitely
>>>> use it just to look at the keys and return a result. Also, as you
>>>> mentioned, Ignite compute is a viable option as well.
>>>>
>>>> The reason that predicates were removed from the get methods is because
>>>> the API was becoming unwary, and also because JCache does not require it.
>>>>
>>>> D.
>>>>
>>>> On Thu, Aug 24, 2017 at 10:50 AM, Andrey Kornev <
>>>> andrewkornev@hotmail.com> wrote:
>>>>
>>>>> Well, I believe invokeAll() has "update" semantics and using it for
>>>>> read-only filtering of cache entries is probably not going to be efficient
>>>>> or even appropriate.
>>>>>
>>>>>
>>>>> I'm afraid the only viable option I'm left with is to use Ignite's
>>>>> Compute feature:
>>>>>
>>>>> - on the sender, group the keys by affinity.
>>>>>
>>>>> - send each group along with the filter predicate to their
>>>>> affinity nodes using IgniteCompute.
>>>>>
>>>>> - on each node, use getAll() to fetch the local keys and apply the
>>>>> filter.
>>>>>
>>>>> - on the sender node, collect the results of the compute jobs into a
>>>>> map.
>>>>>
>>>>>
>>>>> It's unfortunate that Ignite dropped that original API. What used to
>>>>> be a single API call is now a non-trivial algorithm and one have to worry
>>>>> about things like what happens if the grid topology changes while the
>>>>> compute jobs are executing, etc.
>>>>>
>>>>> Can anyone think of any other less complex/more robust approach?
>>>>>
>>>>> Thanks
>>>>> Andrey
>>>>>
>>>>> ------------------------------
>>>>> *From:* slava.koptilin <slava.koptilin@gmail.com>
>>>>> *Sent:* Thursday, August 24, 2017 9:03 AM
>>>>> *To:* user@ignite.apache.org
>>>>> *Subject:* Re: Retrieving multiple keys with filtering
>>>>>
>>>>> Hi Andrey,
>>>>>
>>>>> Yes, you are right. ScanQuery scans all entries.
>>>>> Perhaps, IgniteCache#invokeAll(keys, cacheEntryProcessor) with custom
>>>>> processor will work for you.
>>>>> https://ignite.apache.org/releases/2.1.0/javadoc/org/apache/
>>>>> ignite/IgniteCache.html#invokeAll(java.util.Set,%20org.apach
>>>>> e.ignite.cache.CacheEntryProcessor,%20java.lang.Object...)
>>>>>
>>>>> Thanks!
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> View this message in context: http://apache-ignite-users.705
>>>>> 18.x6.nabble.com/Retrieving-multiple-keys-with-filtering-tp1
>>>>> 6391p16400.html
>>>>> Apache Ignite Users - Retrieving multiple keys with filtering
>>>>> <http://apache-ignite-users.70518.x6.nabble.com/Retrieving-multiple-keys-with-filtering-tp16391p16400.html>
>>>>> apache-ignite-users.70518.x6.nabble.com
>>>>> Retrieving multiple keys with filtering. Hello, I have a list of cache
>>>>> keys (up to a few hundred of them) and a filter predicate. I'd like to
>>>>> efficiently retrieve only those values that pass the...
>>>>>
>>>>>
>>>>> Sent from the Apache Ignite Users mailing list archive at Nabble.com.
>>>>>
>>>>
>>>>
>>>
>>
>

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