Query hint is a better option. Some down side in using this approach: User will have to modify all his query to accommodate this. This won't be session scope but rather query scope On Mon, 9 Oct 2017 at 2:36 AM, jarray <[email protected]> wrote:
> same opinion with @Ravindra，use query hint is better approach ，the syntax > is easy to use > > > > > > > On 10/05/2017 17:10, Rahul Kumar wrote: > @Ravindra Thanks. Using query hint may be better approach. > > I suggest following syntax : > > *select * from t1 [in SEGMENTS(1,3,5)]; * > > Thanks and Regards > > * Rahul Kumar * > > > > On Thu, Oct 5, 2017 at 1:04 PM, Ravindra Pesala <[email protected]> > wrote: > > > Hi, > > > > Instead of using SET command to use for segments why don't you use QUERY > > HINT . Using query hint we can mention the segments inside the query > itself > > as a hint. > > > > For example SELECT /*+SEGMENTS(1,3,5) */ from t1. > > > > By using the above custom hint we can query from selected segments only, > > This concept is supported in Spark also and this concept will be helpful > in > > our any future optimizations > > > > Regards, > > Ravindra. > > > > On 5 October 2017 at 12:22, Rahul Kumar <[email protected]> wrote: > > > > > @Jacky please find the reply of your doubts as follow : > > > > > > > > > *1. If user uses following command in two different beeline session, > > > will there be problem due to multithreading? SET > > > carbon.input.segments.default.* > > > > > > *carbontable=1,3,5; select * from carbontable; SET > > > carbon.input.segments.default.**carbontable=*;* > > > > > > *Ans: *In case of multithreading ,yes there will be problem. > > > > > > So threadSet() can be use to set the same property in multithread > > > mode. > > > * Folowing syntax can be used to set segment ids for multithread > > mode* > > > : > > > Syntax : CarbonSession.threadSet(“carbon.input.segments.< > > > databese_name>.<table_name>”,”<list > > > of segment ids>”) > > > e.g =>*future{* > > > > > > * CarbonSession.threadSet(“**carbon.input.segments. > > > default.carbontable”,”1,3,5”)* > > > > > > * sparkSession.sql(“select * from carbontable”).show* > > > > > > * CarbonSession.threadSet(“carbon.input.segments. > > > default.carbontable”,”*”)* > > > > > > * }* > > > > > > *Above will override the property at thread level. So property will be > > set > > > for each thread .* > > > > > > > > > *2. The RESET command is not clear, why this is needed? It seems SET > > > carbon.input.segments.default.**carbontable=* is enough, right? and > what > > > parameter it has?* > > > > > > *Ans:* RESET command doesn't take any parameter. RESET is already > > > implemented behavior which resets all the properties to their default > > > value.So simillarly RESET query will set the above property also to its > > > default value. > > > > > > Thanks and Regards > > > > > > * Rahul Kumar * > > > > > > > > > > > > On Wed, Oct 4, 2017 at 7:21 PM, Jacky Li <[email protected]> wrote: > > > > > > > I have 2 doubts: > > > > 1. If user uses following command in two different beeline session, > > will > > > > there be problem due to multithreading? > > > > SET carbon.input.segments.default.carbontable=1,3,5; > > > > select * from carbontable; > > > > SET carbon.input.segments.default.carbontable=*; > > > > > > > > > > > > 2. The RESET command is not clear, why this is needed? It seems SET > > > > carbon.input.segments.default.carbontable=* is enough, right? and > what > > > > parameter it has? > > > > > > > > Regards, > > > > Jacky > > > > > > > > > 在 2017年10月4日，上午12:42，Rahul Kumar <[email protected]> 写道： > > > > > > > > > > <segmentReading.odt> > > > > > > > > > > > > > > > > > > > -- > > Thanks & Regards, > > Ravi > > >
