Re: [Discussion]: option to disable multi-layered index scan and use full table scan

Posted by Aniket Adnaik on Sep 28, 2016; 5:50pm
URL: http://apache-carbondata-dev-mailing-list-archive.168.s1.nabble.com/Discussion-option-to-disable-multi-layered-index-scan-and-use-full-table-scan-tp1526p1552.html

In my view we can have both;
1. We should have internal smartness built-in, like databases do based on
cost estimation .Carbon can take simpler approach based on data size or
number of files to scan.
2. Provide some kind of hints OR switch to  enable or disable - MDK, MinMax
and inverted index, individually and together. This would help us in
 testing different scenarios or performance tuning. These are like options
for users who know what they are doing or can be internal options if you we
don't want to create more confusion.

Best Regards,
Aniket

On Tue, Sep 27, 2016 at 11:58 PM, Raghunandan S <
[hidden email]> wrote:

> I agree with jihong.carbon need to have smart logic to decide
> On Wed, 28 Sep 2016 at 6:12 AM, Jihong Ma <[hidden email]> wrote:
>
> > Ideally this should be an internal improvement, not necessarily exposing
> > it as an config option, Carbon should be able to smartly figure out if
> > leveraging index is beneficial or straightly going for a file scan (just
> as
> > Parquet).
> >
> > Regards.
> >
> > Jihong
> >
> > -----Original Message-----
> > From: Liang Big data [mailto:[hidden email]]
> > Sent: Tuesday, September 27, 2016 4:43 PM
> > To: [hidden email]
> > Subject: Re: [Discussion]: option to disable multi-layered index scan and
> > use full table scan
> >
> > Hi
> >
> > good suggestion!
> > Add one configurable option to disable index for no filter and small
> table
> > scenarios.
> > One comment : you are suggesting only disable MDK; How about other
> > index(inverted index,and MINMAX index)?
> >
> > +1 for this feature
> >
> > Regards
> > Liang
> >
> > 2016-09-28 6:49 GMT+08:00 Aniket Adnaik <[hidden email]>:
> >
> > > Carbondata can provide some way to disable usage of multi-layered index
> > and
> > > provide full table scan.
> > > This may help in following cases;
> > > 1. Small tables occupying only few number of blocks are probably better
> > of
> > > using full table scan.
> > > 2. Queries with large number of projections with no filter may benefit
> > from
> > > using full table scan.
> > > 3. Testing different scenarios and comparing with multiple HDFS file
> > > formats
> > > that do not provide multi layer index will be easier.
> > >
> > > Also, Carbondata scan internally should be smart enough to detect this
> > > based
> > > on query, data size, etc.
> > >
> > > Any comments?
> > >
> > >
> > >
> > >
> > > --
> > > View this message in context: http://apache-carbondata-
> > > mailing-list-archive.1130556.n5.nabble.com/Discussion-
> > > option-to-disable-multi-layered-index-scan-and-use-
> > > full-table-scan-tp1526.html
> > > Sent from the Apache CarbonData Mailing List archive mailing list
> archive
> > > at Nabble.com.
> > >
> >
> >
> >
> > --
> >
> > Regards
> > Liang
> >
>