[jira] [Commented] (IMPALA-9176) Make access to null-aware partition from PartitionedHashJoinNode read-only

["Tim Armstrong (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IMPALA-9176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17074137#comment-17074137 ] 

Tim Armstrong commented on IMPALA-9176:
---------------------------------------

Change of plans - the aux structure actually turns out to be significantly slower for some queries, because of the overhead of GetTupleRow(). I'm going to do the alternative approach of multiple iterators into the BTS. I have a prototype that does not require code duplication.

> Make access to null-aware partition from PartitionedHashJoinNode read-only
> --------------------------------------------------------------------------
>
>                 Key: IMPALA-9176
>                 URL: https://issues.apache.org/jira/browse/IMPALA-9176
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Tim Armstrong
>            Assignee: Tim Armstrong
>            Priority: Major
>              Labels: multithreading
>
> Currently the accesses to null_aware_partition() are logically read-only (since the rows and other state is not mutated) and only accesses the build row when pinned, but is implemented using the built-in read iterator of BufferedTupleStream. This would prevent sharing of the build side for null-aware anti-join.
> We need to either allow multiple read iterators for a pinned stream, or build an auxiliary structure, e.g. an array of Tuple ptrs or FlatRowPtr.



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