Gabor Kaszab created IMPALA-11364:
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Summary: Use Late Materialization when structs are in the select
list
Key: IMPALA-11364
URL: https://issues.apache.org/jira/browse/IMPALA-11364
Project: IMPALA
Issue Type: Improvement
Components: Backend
Affects Versions: Impala 4.1.0
Reporter: Gabor Kaszab
IMPALA-9496 introduced querying structs in the select list even for Parquet
tables. However, it has a restriction that in this case late materialization
(LM) can't be used.
The reason is that LM expects the column readers to be used through the batched
reading interface, however, currently struct column readers use the non-batched
reading interface of its children. As a result after reading, the column
readers are not in a state as SkipRows() of LM expects and then results in a
query failure because it's not able to skip the rows for non-filter readers.
Once IMPALA-11363 is implemented and the struct will also use the
ReadValueBatch() interface of its children then late materialization could be
turned on even if structs are in the select list.
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