Sylvain Lebresne created CASSANDRA-7085:
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Summary: Specialized query filters for CQL3
Key: CASSANDRA-7085
URL: https://issues.apache.org/jira/browse/CASSANDRA-7085
Project: Cassandra
Issue Type: Improvement
Reporter: Sylvain Lebresne
Fix For: 3.0
The semantic of CQL makes it so that the current {{NamesQueryFilter}} and
{{SliceQueryFilter}} are not always as efficient as we could be. Namely, when a
{{SELECT}} only selects a handful of columns, we still have to query to query
all the columns of the select rows to distinguish between 'live row but with no
data for the queried columns' and 'no row' (see CASSANDRA-6588 for more
details).
We can solve that however by adding new filters (name and slice) specialized
for CQL. The new name filter would be a list of row prefix + a list of CQL
column names (instead of one list of cell names). The slice filter would still
take a ColumnSlice[] but would add the list of column names we care about for
each row.
The new sstable readers that goes with those filter would use the list of
column names to filter out all the cells we don't care about, so we don't have
to ship those back to the coordinator to skip them there, yet would know to
still return the row marker when necessary.
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