Check Cassandra logs for tombstone threshold error

On Aug 3, 2015 7:32 PM, "Robert Coli" <rcoli@eventbrite.com> wrote:
On Mon, Aug 3, 2015 at 2:48 PM, Sid Tantia <sid.tantia@baseboxsoftware.com> wrote:
Any select all or select count query on a particular table is timing out with "Cassandra::Errors::TimeoutError: Timed out"

A “SELECT * FROM <table> WHERE <partition key> = ‘<partition key value>’ on the table works, but a “SELECT * FROM <table> LIMIT 1; does not work. All other tables and queries work. 

Any ideas as to why this might be happening?

This specific question is getting to be a FAQ...

Briefly : 

1) Cassandra operates best when you supply PRIMARY KEY with your request. 
2) The worst case scenario is therefore SELECT * FROM Table;
3) While SELECT * FROM Table; is trivial in a non-distributed RDBMS, Cassandra is ****NOT A NON-DISTRIBUTED RDBMS**** and so it is NOT TRIVIAL IN CASSANDRA
4) Cassandra is, instead, a distributed data-store in which most operations default to a timeout of fewer than a single digit number of seconds
5) So if SELECTing * FROM your Table is likely to take longer than that, what you'll get is a timeout

The stock remediation for this FAQ is :

a) don't use Cassandra for cases where you need to SELECT * FROM Table
b) if you do have to use it for such a case, use a driver with internal pagination

=Rob