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From Andrey Kornev <andrewkor...@hotmail.com>
Subject Re: Retrieving multiple keys with filtering
Date Thu, 24 Aug 2017 17:50:30 GMT
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.apache.ignite.cache.CacheEntryProcessor,%20java.lang.Object...)

Thanks!



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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...



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