The use case scenario for direct full table scan is rare and not dominating case, the internal built-in smartness should be very cautious about making this decision as this is considered to be in the worst case category. still didn't see a need for exposing it externally.
Regards. Jenny -----Original Message----- From: Aniket Adnaik [mailto:[email protected]] Sent: Wednesday, September 28, 2016 10:50 AM To: [email protected] Subject: Re: [Discussion]: option to disable multi-layered index scan and use full table scan 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 < [email protected]> wrote: > I agree with jihong.carbon need to have smart logic to decide > On Wed, 28 Sep 2016 at 6:12 AM, Jihong Ma <[email protected]> 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:[email protected]] > > Sent: Tuesday, September 27, 2016 4:43 PM > > To: [email protected] > > 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 <[email protected]>: > > > > > 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 > > >
