wjones127 commented on code in PR #15101:
URL: https://github.com/apache/arrow/pull/15101#discussion_r1060902137


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cpp/src/parquet/arrow/reader_writer_benchmark.cc:
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@@ -197,6 +197,52 @@ BENCHMARK_TEMPLATE2(BM_WriteColumn, true, DoubleType);
 BENCHMARK_TEMPLATE2(BM_WriteColumn, false, BooleanType);
 BENCHMARK_TEMPLATE2(BM_WriteColumn, true, BooleanType);
 
+int32_t kInfiniteUniqueValues = -1;
+
+std::shared_ptr<::arrow::Table> RandomStringTable(int64_t length, int64_t 
unique_values,
+                                                  int64_t null_percentage) {
+  std::shared_ptr<::arrow::DataType> type = ::arrow::utf8();
+  std::shared_ptr<::arrow::Array> arr;
+  ::arrow::random::RandomArrayGenerator generator(500);
+  double null_probability = static_cast<double>(null_percentage) / 100.0;
+  if (unique_values == kInfiniteUniqueValues) {
+    arr = generator.String(length, /*min_length=*/3, /*max_length=*/32,
+                           /*null_probability=*/null_probability);
+  } else {
+    arr = generator.StringWithRepeats(length, /*unique=*/unique_values,
+                                      /*min_length=*/3, /*max_length=*/32,
+                                      /*null_probability=*/null_probability);

Review Comment:
   I was thinking it would depending on encoding (dictionary vs PLAIN), and 
IIUC we automatically switch from RLE to plain when we hit a certain threshold 
of unique values. Though perhaps it's sufficient to just benchmark 32 unique 
values and infinite, rather than several different cardinalities. I will also 
make sure to enforce the encoding.



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