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https://issues.apache.org/jira/browse/CASSANDRA-16069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17183171#comment-17183171
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Romain Hardouin commented on CASSANDRA-16069:
---------------------------------------------
IMHO Solution #3 seems the safest solution if it's clearly documented.
Dropping COMPACT STORAGE is not something users do in production without
testing. They must ensure that apps/services work without errors.
If a service relies on this brittle "feature", it will still be able to access
data using a slice query. There is no data unavailability, which is the most
important thing I think.
On top of that, it's not a sneaky change with a silent error. INSERT and UPDATE
will throw InvalidRequest that should appear during tests.
> Loss of functionality around null clustering when dropping compact storage
> --------------------------------------------------------------------------
>
> Key: CASSANDRA-16069
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16069
> Project: Cassandra
> Issue Type: Bug
> Components: Legacy/CQL
> Reporter: Sylvain Lebresne
> Priority: Normal
>
> For backward compatibility reasons[1], it is allowed to insert rows where
> some of the clustering columns are {{null}} for compact tables. That support
> is a tad limited/inconsistent[2] but essentially you can do:
> {noformat}
> cqlsh:ks> CREATE TABLE t (k int, c1 int, c2 int, v int, PRIMARY KEY (k, c1,
> c2)) WITH COMPACT STORAGE;
> cqlsh:ks> INSERT INTO t(k, c1, v) VALUES (1, 1, 1);
> cqlsh:ks> SELECT * FROM t;
> k | c1 | c2 | v
> ---+----+------+---
> 1 | 1 | null | 1
> (1 rows)
> cqlsh:ks> UPDATE t SET v = 2 WHERE k = 1 AND c1 = 1;
> cqlsh:ks> SELECT * FROM t;
> k | c1 | c2 | v
> ---+----+------+---
> 1 | 1 | null | 2
> (1 rows)
> {noformat}
> This is not allowed on non-compact tables however:
> {noformat}
> cqlsh:ks> CREATE TABLE t2 (k int, c1 int, c2 int, v int, PRIMARY KEY (k, c1,
> c2));
> cqlsh:ks> INSERT INTO t2(k, c1, v) VALUES (1, 1, 1);
> InvalidRequest: Error from server: code=2200 [Invalid query] message="Some
> clustering keys are missing: c2"
> cqlsh:ks> UPDATE t2 SET v = 2 WHERE k = 1 AND c1 = 1;
> InvalidRequest: Error from server: code=2200 [Invalid query] message="Some
> clustering keys are missing: c2"
> {noformat}
> Which means that a user with a compact table that rely on this will not be
> able to use {{DROP COMPACT STORAGE}}.
> Which is a problem for the 4.0 upgrade story. Problem to which we need an
> answer.
>
> ----
> [1]: the underlying {{CompositeType}} used by such tables allows to provide
> only a prefix of components, so thrift users could have used such
> functionality. We thus had to support it in CQL, or those users wouldn't have
> been able to upgrade to CQL easily.
> [2]: building on the example above, the value for {{c2}} is essentially
> {{null}}, yet none of the following is currently allowed:
> {noformat}
> cqlsh:ks> INSERT INTO t(k, c1, c2, v) VALUES (1, 1, null, 1);
> InvalidRequest: Error from server: code=2200 [Invalid query] message="Invalid
> null value in condition for column c2"
> cqlsh:ks> UPDATE t SET v = 2 WHERE k = 1 AND c1 = 1 AND c2 = null;
> InvalidRequest: Error from server: code=2200 [Invalid query] message="Invalid
> null value in condition for column c2"
> cqlsh:ks> SELECT * FROM c WHERE k = 1 AND c1 = 1 AND c2 = null;
> InvalidRequest: Error from server: code=2200 [Invalid query] message="Invalid
> null value in condition for column c2"
> {noformat}
> Not only is that unintuitive/inconsistent, but the {{SELECT}} one means there
> is no way to select only the row. You can skip specifying {{c2}} in the
> {{SELECT}}, but this become a slice selection essentially, as shown below:
> {noformat}
> cqlsh:ks> INSERT INTO ct(k, c1, c2, v) VALUES (1, 1, 1, 1);
> cqlsh:ks> SELECT * FROM ct WHERE k = 1 AND c1 = 1;
> k | c1 | c2 | v
> ---+----+------+---
> 1 | 1 | null | 1
> 1 | 1 | 1 | 1
> (2 rows)
> {noformat}
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