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Date: Wed, 15 Apr 2015 20:01:59 +0000 (UTC)
From: "Alex Liu (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Commented] (CASSANDRA-6348) TimeoutException throws if Cql
 query allows data filtering and index is too big and it can't find the data
 in base CF after filtering
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    [ https://issues.apache.org/jira/browse/CASSANDRA-6348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14496805#comment-14496805 ] 

Alex Liu commented on CASSANDRA-6348:
-------------------------------------

Hive has a setting to enable pushdown, by default it's disable. User can enable it if the table has only one indexed column. 


> TimeoutException throws if Cql query allows data filtering and index is too big and it can't find the data in base CF after filtering 
> --------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-6348
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6348
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Alex Liu
>            Assignee: Alex Liu
>         Attachments: 6348.txt
>
>
> If index row is too big, and filtering can't find the match Cql row in base CF, it keep scanning the index row and retrieving base CF until the index row is scanned completely which may take too long and thrift server returns TimeoutException. This is one of the reasons why we shouldn't index a column if the index is too big.
> Multiple indexes merging can resolve the case where there are only EQUAL clauses. (CASSANDRA-6048 addresses it).
> If the query has none-EQUAL clauses, we still need do data filtering which might lead to timeout exception.
> We can either disable those kind of queries or WARN the user that data filtering might lead to timeout exception or OOM.


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