pitrou commented on code in PR #39818:
URL: https://github.com/apache/arrow/pull/39818#discussion_r1472552306
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cpp/src/parquet/column_reader.cc:
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@@ -1478,16 +1480,29 @@ class TypedRecordReader : public
TypedColumnReaderImpl<DType>,
// We skipped the levels by incrementing 'levels_position_'. For values
// we do not have a buffer, so we need to read them and throw them away.
// First we need to figure out how many present/not-null values there are.
- std::shared_ptr<::arrow::ResizableBuffer> valid_bits;
- valid_bits = AllocateBuffer(this->pool_);
-
PARQUET_THROW_NOT_OK(valid_bits->Resize(bit_util::BytesForBits(skipped_records),
- /*shrink_to_fit=*/true));
+ int64_t buffer_size = bit_util::BytesForBits(skipped_records);
+ if (valid_bits_for_skip_ == nullptr) {
+ valid_bits_for_skip_ = AllocateBuffer(this->pool_);
+ }
+ if (buffer_size > valid_bits_for_skip_->size()) {
+ // Increase the bitmap size.
+ PARQUET_THROW_NOT_OK(valid_bits_for_skip_->Resize(
+ std::max<int64_t>(buffer_size, kMaxSkipLevelBufferSize),
+ /*shrink_to_fit=*/false));
+ }
ValidityBitmapInputOutput validity_io;
validity_io.values_read_upper_bound = skipped_records;
- validity_io.valid_bits = valid_bits->mutable_data();
+ validity_io.valid_bits = valid_bits_for_skip_->mutable_data();
validity_io.valid_bits_offset = 0;
DefLevelsToBitmap(def_levels() + start_levels_position, skipped_records,
this->leaf_info_, &validity_io);
+ // If the bitmap is too large, free it to avoid consuming too much memory
when there
Review Comment:
I don't get the point of freeing it, even less of resizing to 0 (??). You
could just resize it to `kMaxSkipLevelBufferSize`.
But really, I would suggest trying a fixed size buffer and working in chunks.
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