[ntuple] improve compression settings access in inspector

root-project · Jan 14, 2025 · 414a240 · 414a240
1 parent 2296923
commit 414a240
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Showing 3 changed files with 23 additions and 7 deletions.
diff --git a/tree/ntupleutil/v7/inc/ROOT/RNTupleInspector.hxx b/tree/ntupleutil/v7/inc/ROOT/RNTupleInspector.hxx
@@ -68,7 +68,7 @@ auto rntuple = std::unique_ptr<RNTuple>(file->Get<RNTuple>("NTupleName"));
 auto inspector = RNTupleInspector::Create(*rntuple);
 
 std::cout << "The compression factor is " << inspector->GetCompressionFactor()
-          << " using compression settings " << inspector->GetCompressionSettings()
+          << " using compression settings " << inspector->GetCompressionSettingsAsString()
           << std::endl;
 ~~~
 */
@@ -135,7 +135,7 @@ public:
 private:
    std::unique_ptr<Internal::RPageSource> fPageSource;
    std::unique_ptr<RNTupleDescriptor> fDescriptor;
-   std::optional<std::uint32_t> fCompressionSettings;
+   std::optional<std::uint32_t> fCompressionSettings; ///< The compression settings are unknown for an empty ntuple
    std::uint64_t fCompressedSize = 0;
    std::uint64_t fUncompressedSize = 0;
 
@@ -210,10 +210,11 @@ public:
    ///
    /// \return The integer representation (\f$algorithm * 10 + level\f$, where \f$algorithm\f$ follows
    /// ROOT::RCompressionSetting::ELevel::EValues) of the compression settings used for the inspected RNTuple.
+   /// Empty for an empty ntuple.
    ///
    /// \note Here, we assume that the compression settings are consistent across all clusters and columns. If this is
    /// not the case, an exception will be thrown when RNTupleInspector::Create is called.
-   int GetCompressionSettings() const { return fCompressionSettings.value(); }
+   std::optional<std::uint32_t> GetCompressionSettings() const { return fCompressionSettings; }
 
    /////////////////////////////////////////////////////////////////////////////
    /// \brief Get a string describing compression settings of the RNTuple being inspected.

diff --git a/tree/ntupleutil/v7/src/RNTupleInspector.cxx b/tree/ntupleutil/v7/src/RNTupleInspector.cxx
@@ -166,8 +166,11 @@ ROOT::Experimental::RNTupleInspector::Create(std::string_view ntupleName, std::s
 
 std::string ROOT::Experimental::RNTupleInspector::GetCompressionSettingsAsString() const
 {
-   int algorithm = fCompressionSettings.value() / 100;
-   int level = fCompressionSettings.value() - (algorithm * 100);
+   if (!fCompressionSettings)
+      return "unknown";
+
+   int algorithm = *fCompressionSettings / 100;
+   int level = *fCompressionSettings - (algorithm * 100);
 
    return RCompressionSetting::AlgorithmToString(static_cast<RCompressionSetting::EAlgorithm::EValues>(algorithm)) +
           " (level " + std::to_string(level) + ")";

diff --git a/tree/ntupleutil/v7/test/ntuple_inspector.cxx b/tree/ntupleutil/v7/test/ntuple_inspector.cxx
@@ -62,7 +62,7 @@ TEST(RNTupleInspector, CompressionSettings)
 
    auto inspector = RNTupleInspector::Create("ntuple", fileGuard.GetPath());
 
-   EXPECT_EQ(207, inspector->GetCompressionSettings());
+   EXPECT_EQ(207, *inspector->GetCompressionSettings());
    EXPECT_EQ("LZMA (level 7)", inspector->GetCompressionSettingsAsString());
 }
 
@@ -94,7 +94,19 @@ TEST(RNTupleInspector, UnknownCompression)
    }
 
    auto inspector = RNTupleInspector::Create("ntuple", fileGuard.GetPath());
-   EXPECT_EQ(505, inspector->GetCompressionSettings());
+   EXPECT_EQ(505, *inspector->GetCompressionSettings());
+}
+
+TEST(RNTupleInspector, Empty)
+{
+   FileRaii fileGuard("test_ntuple_inspector_empty.root");
+   {
+      auto writer = RNTupleWriter::Recreate(RNTupleModel::Create(), "ntuple", fileGuard.GetPath());
+   }
+
+   auto inspector = RNTupleInspector::Create("ntuple", fileGuard.GetPath());
+   EXPECT_FALSE(inspector->GetCompressionSettings());
+   EXPECT_EQ("unknown", inspector->GetCompressionSettingsAsString());
 }
 
 TEST(RNTupleInspector, SizeUncompressedSimple)