On 29 Sep 2009, at 09:57, Mircea Markus wrote:

Hi,

Again, this is a feature from Coherence[1].

Basic idea is to execute a query against the cache, and hold the result object. This result object will always have up to date query result; this means that whenever something is modified in the cache the result itself is updated.

So I'm guessing a use case could be something like putting objects into one node in a cluster and then running a query on a separate node?

Advantage: if one performs the same query very often(e.g. several times every millisecond) the response will be fast and the system will not be overloaded.

E.g.

Filter filter = new AndFilter(new EqualsFilter("getTrader", traderid),
                              new EqualsFilter("getStatus", Status.OPEN));

ContinuousQueryCache cacheOpenTrades = new ContinuousQueryCache(cache, filter);

Iterator iter = cacheOpenTrades.entrySet().iterator(); //*this entrySet call will be instant!*

FOr a full list of scenario in which this can be used take a look at [1].
Shall we consider adding something similar?

I guess it would depend if we were thinking of keeping those iterators. There was the debate about pagination vs iterators so I guess it would depend on what happens with the debate.


Cheers,
Mircea


[1] http://download.oracle.com/docs/cd/E14526_01/coh.350/e14509/continuousquery.htm#BABBEIAH

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