hi Luca, Kylin selectively caches queries those 1. take a lot of time to execute, or 2. scanned a lot of HBase rows The logic is in https://github.com/KylinOLAP/Kylin/blob/0.7.1/server/src/main/java/org/apache/kylin/rest/controller/QueryController.java#L209
In other words, Kylin only caches slow queries. Caching all the query results regardless of its cost is not worth the effort. You can adjust these two parameters kylin.query.cache.threshold.duration and kylin.query.cache.threshold.scancount in kylin.properties to change its behavior On Tue, Jun 16, 2015 at 7:16 PM, Luca Costabello <[email protected]> wrote: > Hello all, > > I am running the 0.7.1-incubating, installed from the release binary. > > Currently, repeated executions of certain queries result in cache hits (as > I expected) > Example: > If I execute twice this query, I get results served from cache the second > time ("hitCache": true): > > SELECT column_1, column_2 > FROM FACT_TABLE > INNER JOIN DIMENSION_TABLE on FACT_TABLE.id = DIMENSION_TABLE.id > WHERE date_ < date'2014-08-31' > GROUP BY column_1, column_2 > > On the other hand, repeated execution of the query below never lead to > cache hits (i.e. I always end up with "hitCache": false). > > SELECT count(*) as total_count > FROM FACT_TABLE > WHERE date_ < date'2014-08-31' > > My use case would highly benefit from extensive caching, since I have few > heavy repeated queries to issue to the system. > I am not familiar with current Kylin cache strategy, and I was wondering if > someone could give me some hints. > Besides, I have not found any cache-related parameter in property files, > aside from kylin.query.cache.enabled in conf/kylin.properties > (kylin.query.cache.enabled is set to true in my case) > > Thanks > > luca > -- Regards, *Bin Mahone | 马洪宾* Apache Kylin: http://kylin.io Github: https://github.com/binmahone
