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From rajesh babu Chintaguntla <chrajeshbab...@gmail.com>
Subject Re: Regarding support to make use of partial covered indexes in scan
Date Thu, 30 Jan 2014 16:19:54 GMT
I will raise tomorrow.
Thanks for quick reply Jesse.

Thanks,
Rajeshbabu.

On Thursday, January 30, 2014, Jesse Yates <jesse.k.yates@gmail.com> 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" <
> rajeshbabu.chintaguntla@huawei.com <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.
> >
> >
> >
> >
> >
> >
> >
>

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