[CASSANDRA-7017] allow per-partition LIMIT clause in cql

• Type: Improvement
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.6
• Labels: cql
• Assignee: Alex Petrov Assign to me
• Reporter: Jonathan Halliday

Authors

Alex Petrov

Reviewers

Sylvain Lebresne

• Created: 09/Apr/14 14:07
• Updated: 16/Apr/19 09:31
• Resolved: 14/Apr/16 09:32

Description

somewhat related to static columns (#6561) and slicing (#4851), it is desirable to apply a LIMIT on a per-partition rather than per-query basis, such as to retrieve the top (most recent, etc) N clustered values for each partition key, e.g.

– for each league, keep a ranked list of users
create table scores (league text, score int, player text, primary key(league, score, player) );

– get the top 3 teams in each league:
select * from scores staticlimit 3;

this currently requires issuing one query per partition key, which is tedious if all the key partition key values are known and impossible if they aren't.

Issue Links

• contains: CASSANDRA-7449 Variation of SELECT DISTINCT to find clustering keys with only static columns
• is related to: CASSANDRA-11535 Add dtests for PER PARTITION LIMIT queries with paging