Thanks a lot guys! On Tue, May 9, 2017 at 7:32 AM, Alexander Dejanovski <a...@thelastpickle.com > wrote:
> Hi Kant, > > Unless you provide the full partition key, I see no way for Cassandra to > avoid doing a full table scan. > In order to know on which specific nodes to search (and in which sstables > ,etc...) it needs to have a token. The token is a hash of the whole > partition key. > For a specific value of column "a" and different values of column "b" you > always end up with different tokens that have no guaranty to be stored on > the same node. > After that, bloom filters, partition indexes, etc... require the full > token too, so a full scan is further necessary on each node to get the > data. > > TL;DR : no way to avoid a full cluster scan unless you provide the full > partition key in your where clause. > > Cheers, > > On Tue, May 9, 2017 at 4:24 PM Jon Haddad <jonathan.had...@gmail.com> > wrote: > >> Nope, I didn’t comment on that query. I specifically answered your >> question about "select * from hello where a='foo' allow filtering;” >> >> The query you’ve listed here looks like it would also do a full table >> scan (again, I don’t see how it would be avoided). >> >> I recommend firing up a 3 node cluster using CCM, creating a key space >> with RF=1, and seeing what it does. >> >> On May 9, 2017, at 9:12 AM, Kant Kodali <k...@peernova.com> wrote: >> >> Hi, >> >> Are you saying The following query select max(b) from hello where a='a1' >> allow filtering; doesn't result in a table scan? I got the result for >> this query and yes I just tried tracing it and looks like it is indeed >> doing a table scan on ReadStage-2 although I am not sure if I am >> interpreting it right? Finally is there anyway to prevent table scan while >> providing the partial partition key and get the max b ? >> >> <Screen Shot 2017-05-09 at 7.07.46 AM.png> >> >> >> >> On Tue, May 9, 2017 at 6:33 AM, Jon Haddad <jonathan.had...@gmail.com> >> wrote: >> >>> I don’t see any way it wouldn’t. Have you tried tracing it? >>> >>> > On May 9, 2017, at 8:32 AM, Kant Kodali <k...@peernova.com> wrote: >>> > >>> > Hi All, >>> > >>> > It looks like Cassandra 3.10 has partial partition key search but does >>> it result in a table scan? for example I can have the following >>> > >>> > create table hello( >>> > a text, >>> > b int, >>> > c text, >>> > d text, >>> > primary key((a,b), c) >>> > ); >>> > >>> > Now I can do select * from hello where a='foo' allow filtering;// This >>> works in 3.10 but I wonder if this query results in table scan and if so is >>> there any way to limit such that I get max b? >>> > >>> > Thanks! >>> >>> >> -- > ----------------- > Alexander Dejanovski > France > @alexanderdeja > > Consultant > Apache Cassandra Consulting > http://www.thelastpickle.com >
