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From "Joshua McKenzie (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-12768) CQL often queries static columns unnecessarily
Date Mon, 17 Oct 2016 21:53:58 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-12768?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Joshua McKenzie updated CASSANDRA-12768:
----------------------------------------
    Reviewer: Tyler Hobbs

> CQL often queries static columns unnecessarily
> ----------------------------------------------
>
>                 Key: CASSANDRA-12768
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12768
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>             Fix For: 3.0.x, 3.x
>
>
> While looking at CASSANDRA-12694 (which isn't directly related, but some of the results
in this ticket are explained by this), I realized that CQL was always querying static columns
even in cases where this is unnecessary.
> More precisely, for reasons long described elsewhere, we have to query all the columns
for a row (we have optimizations, see CASSANDRA-10657, but they don't change that general
fact) to be able to distinguish between the case where a row doesn't exist from when it exists
but has no values for the columns selected by the query. *However*, this really only extend
to "regular" columns (static columns play no role in deciding whether a particular row exists
or not) but the implementation in 3.x, which is in {{ColumnFilter}}, still always query all
static columns.
> We shouldn't do that and it's arguably a performance regression from 2.x. Which is why
I'm tentatively marking this a bug and for the 3.0 line. It's a tiny bit scary for 3.0 though
so really more asking for other opinions and I'd be happy to stick to 3.x.



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