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https://issues.apache.org/jira/browse/CASSANDRA-10352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14747324#comment-14747324
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Sylvain Lebresne commented on CASSANDRA-10352:
----------------------------------------------
I've pushed a fix for this
[here|https://github.com/pcmanus/cassandra/commits/10352]. With that, the dtest
linked above passes.
> Paging with DISTINCT and IN can throw ClassCastException
> --------------------------------------------------------
>
> Key: CASSANDRA-10352
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10352
> Project: Cassandra
> Issue Type: Bug
> Reporter: Sylvain Lebresne
> Assignee: Sylvain Lebresne
> Fix For: 2.1.x, 2.2.x
>
>
> The ctor of {{SliceQueryPager}} has the following code:
> {noformat}
> if (state != null)
> {
> // The only case where this could be a non-CellName Composite is
> if it's Composites.EMPTY, but that's not
> // valid for PagingState.cellName, so we can safely cast to
> CellName.
> lastReturned = (CellName)
> cfm.comparator.fromByteBuffer(state.cellName);
> restoreState(state.remaining, true);
> }
> {noformat}
> The assumption that we can only get a {{CellName}} is invalid however. When
> using a {{MultiPartitionPager}} (so when the query has a {{IN}} on the
> partition key), it's possible for a page to stop at the end of one of the
> underlying pager, and for that pager to be exhausted. If that's the case, the
> {{PagingState}} returned will have the partition key of the next key to
> retrieve, but a {{null}} cellname (since we haven't started to query that
> next key). When the next page is queried, that {{PagingState}} will trigger a
> {{ClassCastException}}.
> The [following
> dtest|https://github.com/pcmanus/cassandra-dtest/commit/b98a112fc22f92aa965d2068345c708ae43b8a85]
> reproduces this problem.
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