Joe McDonnell created IMPALA-13411:
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Summary: DCHECK can fire for scan nodes that produce zero-length
tuples
Key: IMPALA-13411
URL: https://issues.apache.org/jira/browse/IMPALA-13411
Project: IMPALA
Issue Type: Bug
Components: Backend
Affects Versions: Impala 4.5.0
Reporter: Joe McDonnell
This query crashes when using the tuple cache:
{noformat}
select count(*) from functional.alltypes;{noformat}
It hits this assert:
[https://github.com/apache/impala/blob/6121c4f7d61fb9f2341cf14e1be3404325fb35b9/be/src/exec/tuple-file-writer.cc#L105]
{noformat}
DCHECK_GT(tuple_data_len, 0);{noformat}
For this count(*) query, it is not actually returning any columns. Instead,
only the row count matters and the count does not require any tuple data. So,
the tuple data is empty.
We can revisit this DCHECK and either remove it or modify the condition to
check if the tuple size is zero.
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