Offset buffer can be pre-grown in Parquet ByteArray reader (apache#68)

* Offset buffer can be pre-grown in Parquet ByteArray reader * nit
xuechendi · Jun 11, 2020 · 4d166c4 · 4d166c4
1 parent 6f1d8e1
commit 4d166c4
Showing 1 changed file with 12 additions and 1 deletion.
diff --git a/cpp/src/parquet/encoding.cc b/cpp/src/parquet/encoding.cc
@@ -1885,7 +1885,12 @@ class DictByteArrayDecoderImpl : public DictDecoderImpl<ByteArrayType>,
     int32_t indices[kBufferSize];
 
     ArrowBinaryHelper helper(out);
-
+
+    RETURN_NOT_OK(helper.builder->Reserve(num_values));
+    // defaulting to allocating 4 bytes per element
+    RETURN_NOT_OK(helper.builder->ReserveData(
+        std::min<int64_t>(num_values - null_count, helper.chunk_space_remaining)));
+
     arrow::internal::BitmapReader bit_reader(valid_bits, valid_bits_offset, num_values);
 
     auto dict_values = reinterpret_cast<const ByteArray*>(dictionary_->data());
@@ -1948,6 +1953,12 @@ class DictByteArrayDecoderImpl : public DictDecoderImpl<ByteArrayType>,
     int values_decoded = 0;
 
     ArrowBinaryHelper helper(out);
+
+    RETURN_NOT_OK(helper.builder->Reserve(num_values));
+    // defaulting to allocating 4 bytes per element
+    RETURN_NOT_OK(helper.builder->ReserveData(
+        std::min<int64_t>(num_values, helper.chunk_space_remaining)));
+
     auto dict_values = reinterpret_cast<const ByteArray*>(dictionary_->data());
 
     while (values_decoded < num_values) {