[GitHub] [arrow] pitrou commented on a diff in pull request #35691: GH-34785: [C++][Parquet] Skeleton for Parquet bloom filter writer

["pitrou (via GitHub)" <gi...@apache.org>]

pitrou commented on code in PR #35691:
URL: https://github.com/apache/arrow/pull/35691#discussion_r1202627334


##########
cpp/src/parquet/column_writer.cc:
##########
@@ -2299,12 +2319,112 @@ Status TypedColumnWriterImpl<FLBAType>::WriteArrowDense(
   return Status::OK();
 }
 
+template <typename DType>
+void TypedColumnWriterImpl<DType>::UpdateBloomFilter(const T* values,
+                                                     int64_t num_values) {
+  if (bloom_filter_) {
+    for (int64_t i = 0; i < num_values; ++i) {
+      bloom_filter_->InsertHash(bloom_filter_->Hash(values + i));

Review Comment:
   This will be very slow in any case, because there is a double virtual indirection (first `bloom_filter_->Hash`, then `hasher_->Hash`).
   
   I think you want to add batch methods, such as `BloomFilter::InsertHashes(const double* values, int64_t num_values)`.



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