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https://issues.apache.org/jira/browse/CASSANDRA-4915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13492414#comment-13492414
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Sylvain Lebresne commented on CASSANDRA-4915:
---------------------------------------------
Btw, realized that I would be fine about requiring 'ALLOW FULL SCAN' for 2ndary
index queries when we know we suck at them (i.e. when we have a restriction
that is not indexed or for which we don't use the index).
> 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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