Answers inline. On Wed, Aug 19, 2015 at 1:30 PM, Wangfei (X) <[email protected]> wrote:
> > Through reading code, I known some mechanism of LENS. > LENS don’t support CRUD ability on underlying HIVE or JDBC-compatible > physical store. > Yes, you are right wrt native tables. > It set up a metastore on HIVE which is a ROLAP abstract model, we can do > CRUD on this metastore. > Yes. > Query command is another process flow, will first do cost Analysis, then > do rewrite, then send it to selected SQL engine. > > Yes. Query service is different from metastore service. Rewriting the query happens only in case of cube queries. Native queries (queries without cube keyword) are directly passed to driver. If more than one execution engine can pick the query, then Lens picks one with least cost. > Can you help to check whether I’m right? > > 在 2015/8/19 12:47, amareshwarisr . 写道: > > Table and data are not required to be on all stores. The engine is > selected wrt data availability first. Engine is selected on cost basis only > if data is available in more than one store. > > On Wed, Aug 19, 2015 at 10:03 AM, Wangfei (X) <[email protected]> wrote: > >> OK, thanks for your reply. >> I have another problem, >> Lens choose sql engine by cost, so it may send to HIVE or JDBC-compatible >> engine uncertainly. >> So every engine should have the same table schema and same data, how to >> guarantee it? >> >> >> 在 2015/8/19 12:12, amareshwarisr . 写道: >> >> Yes. It can execute, it will fire it on the engine which accepts the >> query - in this case the engine should be able to access the table, then it >> would execute. Basically it will do explain of the query on the engine if >> it passes it will execute. >> >> See sample queries here - >> https://github.com/apache/incubator-lens/blob/master/lens-examples/src/main/resources/dimension-queries.sql >> and >> https://github.com/apache/incubator-lens/blob/master/lens-examples/src/main/resources/cube-queries.sql >> >> Some of the example queries put out there are native queries. >> >> Thanks >> Amareshwari >> >> On Tue, Aug 18, 2015 at 6:55 PM, Wangfei (X) <[email protected]> wrote: >> >>> Hello, I want to ask a question about lens. >>> Does lens support query like "query execute select id,name from >>> dim_table where name != ""first"" " , >>> that is , there is no "cube" keyword in the query, whether this query >>> will send to HIVE or JDBC-Compatible engine, >>> which will not send to OLAP Cube Metastore. I try to find out this >>> problem through reading code, but I'm not sure about it. >>> >> >> >> > >
