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 <dsetrak...@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 <andrewkor...@hotmail.com<mailto:andrewkor...@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.kopti...@gmail.com<mailto:slava.kopti...@gmail.com>> Sent: Thursday, August 24, 2017 9:03 AM To: user@ignite.apache.org<mailto: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! -- View this message in context: http://apache-ignite-users.70518.x6.nabble.com/Retrieving-multiple-keys-with-filtering-tp16391p16400.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<http://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.
