Re: Range scans

[Anuj Wadehra]

Chandra,


I feel that you are trying to implement time series data pattern using 
secondary index and one column per row. I think a much better solution would be 
to partition data based on some logical row key ..if thats not availabke it may 
be hour/day + a bucket id (too prevent hot spots).. You should use timeuuid as 
clustering key and you will be able to query data based on clustering key 
(time) most efficiently..


To understand data modelling of time series data using clustering key, Please 
visit 
https://academy.datastax.com/demos/getting-started-time-series-data-modeling


And


http://intellidzine.blogspot.in/2014/01/cassandra-data-modelling-primary-keys.html?m=1


Thanks

Anuj


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From:"Anuj Wadehra" <anujw_2...@yahoo.co.in>
Date:Thu, 19 Nov, 2015 at 5:31 pm
Subject:Re: Range scans

Hi Chandra,


I will comment on some points. Someone else can take remaining ones:


1. Secondary Index are only useful when data returned by the index query is in 
hundreds. Fetching large data using secondary index would be very slow. 
Secondary indexes dont scale well.


2.token query should be of form:


Where token(key) > «some token»



You are again applying token function on right side of comparison operator and 
thats why 

getting unexpected results.



Thanks

Anuj



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From:"Chandra Sekar KR" <chandraseka...@hotmail.com>
Date:Thu, 19 Nov, 2015 at 3:16 pm
Subject:Range scans

Hi,


I would like to run a range scan on timestamp column b with secondary indexes 
without passing the partition key. I'm aware that Cassandra does not support 
range scans on secondary indexes unless one more column (primary/secondary 
index) clause with an = operator is supplied.


CREATE TABLE test (
    a timeuuid PRIMARY KEY,
    b timestamp,
    c varint
);
CREATE INDEX indx_b ON test (b);


INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000000);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000001);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000002);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000003);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000004);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000005);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000006);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000007);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000008);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000009);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000010);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000011);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000012);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000013);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000014);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000015);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000016);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000017);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000018);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000019);

INSERT INTO TEST(a,b,c) VALUES (now(), unixTimestampOf(now()), 1000020);


Also, is there any alternate way of running range scans on column a using TOKEN 
function, similar to below. I tried running the same, but was getting 
unexpected results.


SELECT * FROM test 

  WHERE TOKEN(a) >= TOKEN(3b84a5b0-8e8d-11e5-b494-c9d29cfa4efd) 

  AND TOKEN(a) <= TOKEN(3b8c94f0-8e8d-11e5-b494-c9d29cfa4efd);


Regards, Chandra Sekar KR