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From "Edward Capriolo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-4915) CQL should force limit when query samples data.
Date Mon, 05 Nov 2012 21:44:12 GMT
Edward Capriolo created CASSANDRA-4915:
------------------------------------------

             Summary: CQL should force limit when query samples data.
                 Key: CASSANDRA-4915
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4915
             Project: Cassandra
          Issue Type: Improvement
    Affects Versions: 1.2.0 beta 1
            Reporter: Edward Capriolo
            Priority: Minor


When issuing a query like:
{noformat}
CREATE TABLE videos (
  videoid uuid,
  videoname varchar,
  username varchar,
  description varchar,
  tags varchar,
  upload_date timestamp,
  PRIMARY KEY (videoid,videoname)
);
SELECT * FROM videos WHERE videoname = 'My funny cat';
{noformat}

Cassandra samples some data using get_range_slice and then applies the query.

This is very confusing to me, because as an end user am not sure if the query is fast because
Cassandra is performing an optimized query (over an index, or using a slicePredicate) or if
cassandra is simple sampling some random rows and returning me some results. 

My suggestions:
1) force people to supply a LIMIT clause on any query that is going to
page over get_range_slice
2) having some type of explain support so I can establish if this
query will work in the

I will champion suggestion 1) because CQL has put itself in a rather unique un-sql like position
by applying an automatic limit clause without the user asking for them. I also do not believe
the CQL language should let the user issue queries that will not work as intended with "larger-then-auto-limit"
size data sets.

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