Henry Manasseh created CASSANDRA-11458:
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Summary: Complete support for CustomExpression
Key: CASSANDRA-11458
URL: https://issues.apache.org/jira/browse/CASSANDRA-11458
Project: Cassandra
Issue Type: Improvement
Components: Core
Reporter: Henry Manasseh
Priority: Minor
This is a proposal to complete the CustomExpression support first introduced as
part of https://issues.apache.org/jira/browse/CASSANDRA-10217.
The current support for custom expressions is partial. There is no clean way to
implement queries making use of the "exp('index', 'value)" syntax due to the
fact CustomExpression is declared as final and there is no way to for
developers to cleanly plug-in their own expressions.
https://github.com/apache/cassandra/blob/6e69c75900f3640195130085ad69daa1659184eb/src/java/org/apache/cassandra/db/filter/RowFilter.java#L869
The proposal is to make CustomExpression not final so that developers can
extend and create their own subclass and provide their own isSatisfiedBy
operation (which currently always returns true).
Introducing a new custom expression would be done as follows:
1. Developer would create a subclass of CustomExpression and override
isSatisfiedBy method with their logic (public boolean isSatisfiedBy(CFMetaData
metadata, DecoratedKey partitionKey, Row row))
2. This class would be packaged in a jar and copied to the cassandra lib
directory along with a secondary index class which overrides
Index.customExpressionValueType
2. Create the custom index with an option which identifies the CustomExpression
subclass (custom_expression_class).
CREATE CUSTOM INDEX ON keyspace.my_table(my_indexed_column) USING
'org.custom.MyCustomIndex'
WITH OPTIONS = { 'custom_expression_class': 'org.custom.MyCustomExpression' };
I have prototyped the change and works as designed. In my case I do a type of
"IN" query filter which will simplify my client logic significantly.
The default behavior of using the CustomExpression class would be maintained if
the developer does not provide a custom class in the create index options.
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