Matt Stump created CASSANDRA-5998:
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Summary: Filters
Key: CASSANDRA-5998
URL: https://issues.apache.org/jira/browse/CASSANDRA-5998
Project: Cassandra
Issue Type: New Feature
Reporter: Matt Stump
As a counterpart to the functionality provided in triggers it is desirable to
filter/mutate query results utilizing a user specified classes.
Some example use cases include:
Row or cell level permissions
Ad-hoc aggregation or filtering of column values
Proposed changes include the following:
* Alter CF metadata to allow the specification of filter classes and options.
* Modification of the CQL(3) grammar and addition of create/drop filter
statements to allow the specification of filter classes.
* Move cassandara/triggers/CustomClassLoader.java to
cassandara/CustomClassLoader.java and use the class loader for both triggers
and filters.
* The addition of the following classes: FilterDefinition, FilterExecuter, and
IFilter.
* Modification of StorageProxy::fetchRows, such that if the CF has a filter
specified, rows returned by the result set are run first through the filter
which has the authority of either dropping or modifying rows from the result
set. If no filter is specified then no filter will be invoked.
* In order to enable the row/cell level authorization use case
StorageProxy::fetchRows must be modified to also require the ClientState.
Risks:
My main concern with the current proposal is that the dependency on ClientState
in order to satisfy the cell/row level permissions use case will introduce
tight coupling between StorageProxy and ClientState. Another possibility yet to
be investigated is to pass ClientState to the filter when the filter class is
instantiated.
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