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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