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https://issues.apache.org/jira/browse/IMPALA-15387?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aleksandr Efimov resolved IMPALA-15387.
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Fix Version/s: Impala 5.0.0
Resolution: Fixed
> Parquet: two nested levels return the next row's values in later row groups
> ---------------------------------------------------------------------------
>
> Key: IMPALA-15387
> URL: https://issues.apache.org/jira/browse/IMPALA-15387
> Project: IMPALA
> Issue Type: Bug
> Components: Backend
> Affects Versions: Impala 5.0.0
> Reporter: Aleksandr Efimov
> Assignee: Aleksandr Efimov
> Priority: Critical
> Labels: correctness
> Fix For: Impala 5.0.0
>
>
> Since IMPALA-3841, reading two nested levels can return a scalar field of the
> next top-level row, silently. It starts at the first page boundary of the
> second or a later row group. We hit it on production data.
> {code:sql}
> select count(*), count(o.o_orderkey), sum(o.o_orderkey)
> from customer_nested_multiblock_multipage c
> left join c.c_orders o
> left join o.o_lineitems l;
> -- expected (pyarrow): 11908, 11808, 34964524398
> -- actual: 11908, 9964, 29547222652
> {code}
> One level ({{left join c.c_orders o}}) is correct.
> Cause: ComplexColumnReader::Reset() does not clear next_levels_consumed_. The
> first NextLevels() of c_orders in a new row group skips o_lineitems, treats
> c_orders as empty and reads levels again, so o_orderkey reads its levels
> twice. At the next page boundary it drops one value and is one row ahead from
> then on.
> Fix: clear next_levels_consumed_ in Reset().
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