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[ntuple] Account for aliased pages in on-disk size calculation #19460

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[ntuple] Account for aliased pages in on-disk size calculation #19460

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690c234
[ntuple] Account for aliased pages in inspector size calculation
enirolf Jul 25, 2025
7ecc797
[ntuple] Account for aliased pages in `RNTupleDescriptor::PrintInfo`
enirolf Jul 25, 2025
7a2ced9
[ntuple] Distinguish between physical and aliased pages
enirolf Jul 25, 2025
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11 changes: 10 additions & 1 deletion tree/ntupleutil/v7/src/RNTupleInspector.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,7 @@ void ROOT::Experimental::RNTupleInspector::CollectColumnInfo()
// to report the size _in memory_ of column elements.
std::uint32_t elemSize = RColumnElementBase::Generate(colDesc.GetType())->GetSize();
std::uint64_t nElems = 0;
std::unordered_set<std::uint64_t> seenPages{};
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I think you can move the map down into the first level of the for loop because we don't deduplicate pages across clusters. This will also limit the memory used for the map.

std::vector<std::uint64_t> compressedPageSizes{};

for (const auto &clusterDescriptor : fDescriptor.GetClusterIterable()) {
Expand Down Expand Up @@ -88,8 +89,16 @@ void ROOT::Experimental::RNTupleInspector::CollectColumnInfo()

const auto &pageRange = clusterDescriptor.GetPageRange(colId);

std::uint64_t locatorOffset;
for (const auto &page : pageRange.GetPageInfos()) {
compressedPageSizes.emplace_back(page.GetLocator().GetNBytesOnStorage());
locatorOffset = page.GetLocator().GetType() == ROOT::RNTupleLocator::ELocatorType::kTypeDAOS
? page.GetLocator().GetPosition<RNTupleLocatorObject64>().GetLocation()
: page.GetLocator().GetPosition<std::uint64_t>();
auto [_, pageAdded] = seenPages.emplace(locatorOffset);
if (pageAdded) {
compressedPageSizes.emplace_back(page.GetLocator().GetNBytesOnStorage());
}
// For the moment, we actually load and decompress aliased pages multiple times
fUncompressedSize += page.GetNElements() * elemSize;
}
}
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24 changes: 24 additions & 0 deletions tree/ntupleutil/v7/test/ntuple_inspector.cxx
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Expand Up @@ -263,6 +263,30 @@ TEST(RNTupleInspector, SizeProjectedFields)
EXPECT_EQ(inspector->GetFieldTreeInspector("muonPt").GetCompressedSize(), inspector->GetCompressedSize());
}

TEST(RNTupleInspector, SizeSamePageMerging)
{
FileRaii fileGuard("test_ntuple_inspector_size_same_page_merging.root");
{
auto model = RNTupleModel::Create();
auto nFldInt = model->MakeField<std::int32_t>("int");

auto writeOptions = RNTupleWriteOptions();
writeOptions.SetCompression(0);
writeOptions.SetInitialUnzippedPageSize(16);
writeOptions.SetMaxUnzippedPageSize(16);
auto ntuple = RNTupleWriter::Recreate(std::move(model), "ntuple", fileGuard.GetPath(), writeOptions);

for (int32_t i = 0; i < 64; ++i) {
*nFldInt = 0;
ntuple->Fill();
}
}

auto inspector = RNTupleInspector::Create("ntuple", fileGuard.GetPath());
EXPECT_EQ(inspector->GetUncompressedSize(), 256);
EXPECT_EQ(inspector->GetCompressedSize(), 16);
}

TEST(RNTupleInspector, ColumnInfoCompressed)
{
FileRaii fileGuard("test_ntuple_inspector_column_info_compressed.root");
Expand Down