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/index.html?javax/cache/processor/EntryProcessor.html D. On Mon, Aug 28, 2017 at 8:29 PM, Andrey Kornev <andrewkor...@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 <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> > 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> >> *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! >> >> >> >> -- >> View this message in context: http://apache-ignite-users.705 >> 18.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 >> 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. >> > >
