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https://issues.apache.org/jira/browse/CASSANDRA-4915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13498239#comment-13498239
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Edward Capriolo commented on CASSANDRA-4915:
--------------------------------------------
I am unclear on what "WITH FILTERING ALLOWED" does. Is it a clause that must be
applied to let this query run? Or is it a clause that changes how the query
runs?
SELECT * FROM videos WHERE videoname = 'My funny cat' WITH FILTERING ALLOWED;
SELECT * FROM videos WHERE videoname = 'My funny cat' ;
I do agree that LIMIT is the wrong concept because that limits the result set
and that will not short-circuit a query.
A better syntax could be this:
SELECT * FROM videos WHERE videoname = 'My funny cat' WITH MAX_EXAMINED = 5;
Where MAX_EXAMINED would be a count of columns/rows? processed. Whenever we
iterate over more then MAX_EXAMINED we shout circuit and return what we have.
(which may be nothing)
> CQL should prevent or warn about inefficient queries
> ----------------------------------------------------
>
> 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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