Through reading code, I known some mechanism of LENS.
LENS don’t support CRUD ability on underlying HIVE or JDBC-compatible
physical store.
It set up a metastore on HIVE which is a ROLAP abstract model, we can do
CRUD on this metastore.
Query command is another process flow, will first do cost Analysis, then
do rewrite, then send it to selected SQL engine.
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]
<mailto:[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]
<mailto:[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.
