Edward Capriolo created CASSANDRA-4915:
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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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