Zoltán Borók-Nagy created IMPALA-11134:
------------------------------------------
Summary: Impala returns "Couldn't skip rows in file" error for old
Parquet file
Key: IMPALA-11134
URL: https://issues.apache.org/jira/browse/IMPALA-11134
Project: IMPALA
Issue Type: Bug
Reporter: Zoltán Borók-Nagy
Impala returns "Couldn't skip rows in file" error for old Parquet file written
by an old Impala (e.g. Impala 2.5, 2.6)
In DEBUG build Impala crashes by a DCHECK:
{noformat}
F0217 18:21:34.449540 24288 parquet-column-readers.cc:1611]
d3407555528be8a8:5ea3fceb00000001] Check failed: num_buffered_values_ > 0 (-1
vs. 0)
{noformat}
The problem is that in some old Parquet files there can be a mismatch between
'num_values' in a page and the encoded def/rep levels. There is usually one
more def/rep levels encoded in these files.
In SkipTopLevelRows() we skip values based on how many def levels left:
https://github.com/apache/impala/blob/92ce6fe48e75d7780efe9a275122554e59aac916/be/src/exec/parquet/parquet-column-readers.cc#L1308-L1314
Since there are more def levels than values, {{num_buferred_values_}} becomes
{{-1}}. I looked at Parquet files written by newer Impala and the number of def
levels matches the number of values.
The workaround is fairly easy, we could also take the value of
num_buferred_values_ into account when calculating 'read_count', i.e.
min(min(num_buffered_values_, num_rows - i), repeated_run_length); so we can
deal with such files.
--
This message was sent by Atlassian Jira
(v8.20.1#820001)
