Continuously fields can read by one system call in BlobStore::read

[flowbehappy]

Enhancement

To avoid too many IOPS.

tiflash/dbms/src/Storages/Page/V3/BlobStore.cpp

Lines 633 to 638 in e3a4412

	for (const auto field_index : fields)
	{
	// TODO: Continuously fields can read by one system call.
	const auto [beg_offset, end_offset] = entry.getFieldOffsets(field_index);
	const auto size_to_read = end_offset - beg_offset;
	auto blob_file = read(entry.file_id, entry.offset + beg_offset, write_offset, size_to_read, read_limiter);

[yy782]

/assign