Pardeep Singh created CASSANDRA-6509:
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Summary: CQL collection list throws error on delete (hiding the
error will help)
Key: CASSANDRA-6509
URL: https://issues.apache.org/jira/browse/CASSANDRA-6509
Project: Cassandra
Issue Type: Improvement
Reporter: Pardeep Singh
Priority: Minor
Currently as of CQL 3.1, collection list query throws error.
DELETE scores[1] FROM plays WHERE id = '123-afde'; // deletes
the 2nd element of scores (raises an error is scores has less than 2 elements)
The above query is not an issue for single queries since I can ignore the
error. But if I do a batch, the above query will fail and the batch will fail
also.
I was trying to accomplish this:
BEGIN UNLOGGED BATCH
DELETE scores[499] FROM plays WHERE id = '123-afde';
DELETE scores[499] FROM plays WHERE id = '144-afde';
APPLY BATCH;
My main goal is to keep a list of 500 recent posts, delete the rest. So I'm
insert to list by prepending an ID, then deleting from the end of the list. I
can deal with it if the list is not exact 500 posts, the point is to keep it
close to that number.
I'm doing this in bulk so using BATCH helps improve performance and I'm also
using UNLOGGED since deleting is not critical part of the process.
By not throwing error on the above query, other use cases can be implemented:
BEGIN UNLOGGED BATCH
DELETE scores[499] FROM plays WHERE id = 'aaa';
UPDATE scores=[2]+scores WHERE id='aaa';
APPLY BATCH;
By using atomic BATCH, I can cap the list at 500 elements.
It would help, even if you can provide a way to bypass the delete error using
some special directive so the BATCH can still be processed.
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