[GitHub] [arrow] emkornfield commented on a change in pull request #8203: ARROW-10024: [C++][Parquet] Create nested reading benchmarks

[GitBox <gi...@apache.org>]

emkornfield commented on a change in pull request #8203:
URL: https://github.com/apache/arrow/pull/8203#discussion_r489538445



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File path: cpp/src/arrow/testing/random.cc
##########
@@ -250,12 +267,20 @@ std::shared_ptr<Array> RandomArrayGenerator::StringWithRepeats(int64_t size,
 }
 
 std::shared_ptr<Array> RandomArrayGenerator::Offsets(int64_t size, int32_t first_offset,
-                                                     int32_t last_offset) {
+                                                     int32_t last_offset,
+                                                     double null_probability) {
   using GenOpt = GenerateOptions<int32_t, std::uniform_int_distribution<int32_t>>;
-  GenOpt options(seed(), first_offset, last_offset, /*null_probability=*/0);
+  GenOpt options(seed(), first_offset, last_offset, null_probability);
 
   BufferVector buffers{2};
 
+  int64_t null_count = 0;
+  buffers[0] = *AllocateEmptyBitmap(size);
+  options.GenerateBitmap(buffers[0]->mutable_data(), size, &null_count);
+  // Make sure the first and last entry are non-null

Review comment:
       why is this important?




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