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Sylvain Lebresne commented on CASSANDRA-12768:
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I rebased the branches (no change), but maybe a gentle ping for review and this
kind of block CASSANDRA-12694 right now (we could do without this, but it's
better with it and it's easy enough I feel).
> 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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