I will raise tomorrow. Thanks for quick reply Jesse. Thanks, Rajeshbabu.
On Thursday, January 30, 2014, Jesse Yates <[email protected]> wrote: > AFAIK, no one is working on this, but it sounds pretty cool! > > Mind filling a JIRA? > > Thanks, > J > On Jan 30, 2014 7:28 AM, "rajeshbabu chintaguntla" < > [email protected] <javascript:;>> wrote: > > > Hi, > > > > Normally when we want to use secondary indices we create index on one or > > very few > > columns of interest in query conditions. Index may not contain all the > > columns to retrieve. > > > > Currently Phoenix supporting full covered indexes only(where all or most > > of the columns > > should be in the index in many cases). When we run a query we will choose > > to scan from user table > > or index table based on condition that whether all projected columns in > > the index or not. > > This approach may have some disadvantages mainly in case of wider tables. > > 1)If we did just store all the columns in the index, then it would be > just > > like creating another copy of the entire table > > - which would take up way too much space and would be very inefficient > > for wider tables. > > 2) Some times if user creates index on few columns and observes that > index > > is not getting used > > and then he need to add all the projected columns to index(may be to the > > part of index or included columns). > > which is something like we are exposing design decisions to the users, > > especially when we already > > target to simplify user's experience by giving SQL on top of a noSQL DB. > > 3) One more thing is as of now if we have an index table contains all > > projected columns in the > > query then we are simply scanning index table only.This can also become > > full table scan when we don't > > have any condition in the query or condition on non primary key column of > > index. > > Some times this might give bad performance than normal table full scan. > > > > Any one working to make use of partial covered indexes to avoid full > table > > scan? > > > > We are interested to work on this in Phoenix. > > > > As part of our local indexing solution, we have similar kind of support. > > From index table first we fetch main table row key and from that we get > > projected columns data from main table so that we can skip most of > records > > to scan from main table. > > > > Thanks, > > Rajeshbabu. > > > > > > > > > > > > > > >
