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https://issues.apache.org/jira/browse/CASSANDRA-12127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15359730#comment-15359730
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Alex Petrov commented on CASSANDRA-12127:
-----------------------------------------
Great find & investigation!
The behaviour of {{2.1}} / {{2.2}} can be explained by (leaving the class cast
aside) the fact that there's no distinction between not specifying the
clustering slice at all and specifying the empty buffer (therefore in both
cases 2 rows are returned). Empty buffer would get translated to
{{Composites#EMPTY}} and afterwards get discarded by
{{AtomicBTreeColumns#slice}} as it checks for {{isEmpty}} and replaces all
empty bounds with {{null}}.
Semantically, {{>}} with empty byte buffer would be same as specifying no
condition at all, and in case with {{<}} (same as {{=}}) result is more or less
known in advance: no results.
> Queries with empty ByteBuffer values in clustering column restrictions fail
> for non-composite compact tables
> ------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-12127
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12127
> Project: Cassandra
> Issue Type: Bug
> Reporter: Benjamin Lerer
> Assignee: Benjamin Lerer
>
> For the following table:
> {code}
> CREATE TABLE myTable (pk int,
> c blob,
> value int,
> PRIMARY KEY (pk, c)) WITH COMPACT STORAGE;
> INSERT INTO myTable (pk, c, value) VALUES (1, textAsBlob('1'), 1);
> INSERT INTO myTable (pk, c, value) VALUES (1, textAsBlob('2'), 2);
> {code}
> The query: {{SELECT * FROM myTable WHERE pk = 1 AND c > textAsBlob('');}}
> Will result in the following Exception:
> {code}
> java.lang.ClassCastException:
> org.apache.cassandra.db.composites.Composites$EmptyComposite cannot be cast
> to org.apache.cassandra.db.composites.CellName
> at
> org.apache.cassandra.db.composites.AbstractCellNameType.cellFromByteBuffer(AbstractCellNameType.java:188)
> at
> org.apache.cassandra.db.composites.AbstractSimpleCellNameType.makeCellName(AbstractSimpleCellNameType.java:125)
> at
> org.apache.cassandra.db.composites.AbstractCellNameType.makeCellName(AbstractCellNameType.java:254)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.makeExclusiveSliceBound(SelectStatement.java:1206)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.applySliceRestriction(SelectStatement.java:1214)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.processColumnFamily(SelectStatement.java:1292)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.process(SelectStatement.java:1259)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.processResults(SelectStatement.java:299)
> [...]
> {code}
> The query: {{SELECT * FROM myTable WHERE pk = 1 AND c < textAsBlob('');}}
> Will return 2 rows instead of 0.
> The query: {{SELECT * FROM myTable WHERE pk = 1 AND c = textAsBlob('');}}
> {code}
> java.lang.AssertionError
> at
> org.apache.cassandra.db.composites.SimpleDenseCellNameType.create(SimpleDenseCellNameType.java:60)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.addSelectedColumns(SelectStatement.java:853)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.getRequestedColumns(SelectStatement.java:846)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.makeFilter(SelectStatement.java:583)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.getSliceCommands(SelectStatement.java:383)
> at
> org.apache.cassandra.cql3.statements.SelectStatement.getPageableCommand(SelectStatement.java:253)
> [...]
> {code}
> I checked 2.0 and {{SELECT * FROM myTable WHERE pk = 1 AND c >
> textAsBlob('');}} works properly but {{SELECT * FROM myTable WHERE pk = 1 AND
> c < textAsBlob('');}} return the same wrong results than in 2.1.
> The {{SELECT * FROM myTable WHERE pk = 1 AND c = textAsBlob('');}} is
> rejected if a clear error message: {{Invalid empty value for clustering
> column of COMPACT TABLE}}.
> As it is not possible to insert an empty ByteBuffer value within the
> clustering column of a non-composite compact tables those queries do not
> have a lot of meaning. {{SELECT * FROM myTable WHERE pk = 1 AND c <
> textAsBlob('');}} and {{SELECT * FROM myTable WHERE pk = 1 AND c =
> textAsBlob('');}} will return nothing
> and {{SELECT * FROM myTable WHERE pk = 1 AND c > textAsBlob('');}} will
> return the entire partition (pk = 1).
> In my opinion those queries should probably all be rejected as it seems that
> the fact that {{SELECT * FROM myTable WHERE pk = 1 AND c > textAsBlob('');}}
> was accepted in {{2.0}} was due to a bug.
> I am of course open to discussion.
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