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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8254) Query parameters (and more) are limited to 65,536 entries
Date Tue, 04 Nov 2014 21:44:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8254?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14196887#comment-14196887
] 

Tyler Hobbs commented on CASSANDRA-8254:
----------------------------------------

bq. It feels to me that to cope with such situation it would be more elegant to allow for
a single parameter that would be something like a List<Tuple<?>>. Going beyond
65k parameters feels odd to me, even in this relevant situation.

We do currently accept a single query parameter of type list<tuple<...>> for this.
 I would suggest using that instead of changing the protocol to support more than 65k query
parameters.

> Query parameters (and more) are limited to 65,536 entries
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-8254
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8254
>             Project: Cassandra
>          Issue Type: Bug
>          Components: API
>            Reporter: Nicolas Favre-Felix
>
> Parameterized queries are sent over the wire as a string followed by a list of arguments.
This list is decoded in QueryOptions.Codec by CBUtil.readValueList(body), which in turn reads
a 16-bit short value from the wire as the number of values to deserialize.
> Sending more values leads to a silent overflow, sometimes reported by the driver as a
protocol error as other values are deserialized incorrectly.
> 64k sounds like a lot, but tables with a large number of clustering dimensions can hit
this limit when fetching a few thousand CQL rows only with an IN query, e.g.
> {code}
> SELECT * FROM sensor_data WHERE a=? and (b,c,d,e,f,g,h,i) IN ((?,?,?,?,?,?,?,?), (?,?,?,?,?,?,?,?),
(?,?,?,?,?,?,?,?), (?,?,?,?,?,?,?,?) ... )
> {code}
> Here, having 8 dimensions in the clustering key plus 1 in the partitioning key restricts
the read to 8,191 CQL rows.
> Some other parts of Cassandra still use 16-bit sizes, for example preventing users to
fetch all elements of a large collection (CASSANDRA-6428). The suggestion at the time was
"we'll fix it in the next iteration of the binary protocol", so I'd like to suggest switching
to variable-length integers as this would solve such issues while keeping messages short.



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