[jira] [Created] (ARROW-10377) [C++][Parquet] nullptr access violation when writing arrays of non-nullable values

[Tanguy Fautre (Jira)]

Tanguy Fautre created ARROW-10377:
-------------------------------------

             Summary: [C++][Parquet] nullptr access violation when writing 
arrays of non-nullable values
                 Key: ARROW-10377
                 URL: https://issues.apache.org/jira/browse/ARROW-10377
             Project: Apache Arrow
          Issue Type: Bug
    Affects Versions: 2.0.0
            Reporter: Tanguy Fautre


I'm updating ParquetSharp to build against Arrow 2.0.0 (currently using Arrow 
1.0.1). One of our unit test is now throwing a {{nullptr}} access violation.

I have narrowed it down to writing arrays of non-nullable values (in this case 
the column contains {{int[]}}) . If the values are nullable, the test passes.

The test crashes when calling {{TypedColumnWriter::WriteBatchSpaced}} with the 
following  arguments:
* {{num_values = 1}}
* {{def_levels = {0}}}
* {{rep_levels = {0}}}
* {{valid_bits = {0}}}
* {{valid_bit_offset = 0}}
* {{values = {}}}

This call is effectively trying to write a null array, and therefore (to my 
understanding) does not need to pass any values and sets {{values = nullptr}}.

I believe the problem lies with
{code:c++}
  void MaybeCalculateValidityBits(
    const int16_t* def_levels,
    int64_t batch_size,
    int64_t* out_values_to_write,
    int64_t* out_spaced_values_to_write,
    int64_t* null_count) {
    if (bits_buffer_ == nullptr) {
      if (!level_info_.HasNullableValues()) {
        *out_values_to_write = batch_size;
        *out_spaced_values_to_write = batch_size;
        *null_count = 0;
      } else {
        for (int x = 0; x < batch_size; x++) {
          *out_values_to_write += def_levels[x] == level_info_.def_level ? 1 : 
0;
          *out_spaced_values_to_write +=
              def_levels[x] >= level_info_.repeated_ancestor_def_level ? 1 : 0;
        }
        *null_count = *out_values_to_write - *out_spaced_values_to_write;
      }
      return;
    }

    // ...
  }
{code}

In particular, {{level_info_.HasNullableValues()}} returns {{false}} given that 
the arrays cannot contain null-values. My understanding is that this is wrong, 
since the arrays themselves are nullable.



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