Sylvain Lebresne created CASSANDRA-6783:
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Summary: Collections should have a proper compare() method for UDT
Key: CASSANDRA-6783
URL: https://issues.apache.org/jira/browse/CASSANDRA-6783
Project: Cassandra
Issue Type: Bug
Reporter: Sylvain Lebresne
Assignee: Sylvain Lebresne
Fix For: 2.1 beta2
So far, ListType, SetType and MapType don't have a proper implementation of
compare() (they throw UnsupportedOperationException) because we haven't need
one since as far as the cell comparator is concenred, only parts of a
collection ends up in the comparator and need to be compared, but the full
collection itself does not.
But with UDT can nest a collection and that sometimes require to be able to
compare them. Typically, I pushed a dtest
[here|https://github.com/riptano/cassandra-dtest/commit/290e9496d1b2c45158c7d7f5487d09ba48897a7f]
that ends up throwing:
{noformat}
java.lang.UnsupportedOperationException: CollectionType should not be use
directly as a comparator
at
org.apache.cassandra.db.marshal.CollectionType.compare(CollectionType.java:72)
~[main/:na]
at
org.apache.cassandra.db.marshal.CollectionType.compare(CollectionType.java:37)
~[main/:na]
at
org.apache.cassandra.db.marshal.AbstractType.compareCollectionMembers(AbstractType.java:174)
~[main/:na]
at
org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:101)
~[main/:na]
at
org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:35)
~[main/:na]
at java.util.TreeMap.compare(TreeMap.java:1188) ~[na:1.7.0_45]
at java.util.TreeMap.put(TreeMap.java:531) ~[na:1.7.0_45]
at java.util.TreeSet.add(TreeSet.java:255) ~[na:1.7.0_45]
at org.apache.cassandra.cql3.Sets$DelayedValue.bind(Sets.java:205)
~[main/:na]
at org.apache.cassandra.cql3.Sets$Literal.prepare(Sets.java:91)
~[main/:na]
at
org.apache.cassandra.cql3.UserTypes$Literal.prepare(UserTypes.java:60)
~[main/:na]
at
org.apache.cassandra.cql3.Operation$SetElement.prepare(Operation.java:221)
~[main/:na]
at
org.apache.cassandra.cql3.statements.UpdateStatement$ParsedUpdate.prepareInternal(UpdateStatement.java:201)
~[main/:na]
...
{noformat}
Note that this stack doesn't involve cell name comparison at all, it's just
that CQL3 sometimes uses a SortedSet underneath to deal with set literals
(since internal sets are sorted by their value), and so when a set contains UDT
that has set themselves, we need the collection comparison. That being said,
for some cases like having a UDT as a map key, we do would need collections to
be comparable for the purpose of cell name comparison.
Attaching relatively simple patch. The patch is a bit bigger than it should be
because while adding the 3 simple compare() method, I realized that we had
methods to read a short length (2 unsigned short) from a ByteBuffer duplicated
all over the place and that it was time to consolidate that in ByteBufferUtil
where it should have been from day one (thus removing the duplication). I can
separate that trivial refactor in a separate patch if we really need to, but
really, the new stuff is the compare() method implementation in ListType,
SetType and MapType and the rest is a bit of trivial cleanup.
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