Add new Tablet API to expose optionalSections metadata (#125)

Summary:

This new API will unlock use cases such as enumerating all optional sections in the Nimble file. It will also empower `nimble_dump` to be able to provide relevant information about the optional sections.

Differential Revision: D67949242

dwio/nimble/common/Types.h

@@ -130,6 +130,32 @@ enum class CompressionType : uint8_t {
   MetaInternal = 2,
 };
 
+class MetadataSection {
+ public:
+  MetadataSection(
+      uint64_t offset,
+      uint32_t size,
+      CompressionType compressionType)
+      : offset_(offset), size_(size), compressionType_(compressionType) {}
+
+  uint64_t offset() const {
+    return offset_;
+  }
+
+  uint32_t size() const {
+    return size_;
+  }
+
+  CompressionType compressionType() const {
+    return compressionType_;
+  }
+
+ private:
+  uint64_t offset_;
+  uint32_t size_;
+  CompressionType compressionType_;
+};
+
 std::string toString(CompressionType compressionType);
 std::ostream& operator<<(std::ostream& out, CompressionType compressionType);
 

dwio/nimble/tablet/TabletReader.cpp

@@ -18,6 +18,7 @@
 #include "dwio/nimble/common/Buffer.h"
 #include "dwio/nimble/common/EncodingPrimitives.h"
 #include "dwio/nimble/common/Exceptions.h"
+#include "dwio/nimble/common/Types.h"
 #include "dwio/nimble/tablet/Compression.h"
 #include "dwio/nimble/tablet/Constants.h"
 #include "dwio/nimble/tablet/FooterGenerated.h"
@@ -383,7 +384,7 @@ TabletReader::TabletReader(
     for (auto i = 0; i < optionalSections->names()->size(); ++i) {
       optionalSections_.insert(std::make_pair(
           optionalSections->names()->GetAsString(i)->str(),
-          std::make_tuple(
+          MetadataSection(
               optionalSections->offsets()->Get(i),
               optionalSections->sizes()->Get(i),
               static_cast<CompressionType>(
@@ -399,9 +400,9 @@ TabletReader::TabletReader(
       continue;
     }
 
-    const auto sectionOffset = std::get<0>(it->second);
-    const auto sectionSize = std::get<1>(it->second);
-    const auto sectionCompressionType = std::get<2>(it->second);
+    const auto sectionOffset = it->second.offset();
+    const auto sectionSize = it->second.size();
+    const auto sectionCompressionType = it->second.compressionType();
 
     if (sectionOffset < offset) {
       // Section was not read yet. Need to read from file.
@@ -427,7 +428,7 @@ TabletReader::TabletReader(
       auto iobuf = std::move(result[i]);
       const std::string preload{mustRead[i].label};
       auto metadata = std::make_unique<MetadataBuffer>(
-          memoryPool_, iobuf, std::get<2>(optionalSections_[preload]));
+          memoryPool_, iobuf, optionalSections_.at(preload).compressionType());
       optionalSectionsCache_.wlock()->insert({preload, std::move(metadata)});
     }
   }
@@ -670,9 +671,9 @@ std::optional<Section> TabletReader::loadOptionalSection(
     return std::nullopt;
   }
 
-  const auto offset = std::get<0>(it->second);
-  const auto size = std::get<1>(it->second);
-  const auto compressionType = std::get<2>(it->second);
+  const auto offset = it->second.offset();
+  const auto size = it->second.size();
+  const auto compressionType = it->second.compressionType();
 
   velox::common::Region region{offset, size, name};
   folly::IOBuf iobuf;

dwio/nimble/tablet/TabletReader.h

@@ -17,6 +17,7 @@
 #include <span>
 
 #include "dwio/nimble/common/Checksum.h"
+#include "dwio/nimble/common/Types.h"
 #include "dwio/nimble/common/Vector.h"
 #include "folly/Range.h"
 #include "folly/Synchronized.h"
@@ -251,6 +252,10 @@ class TabletReader {
       const StripeIdentifier& stripe,
       std::span<const uint32_t> streamIdentifiers) const;
 
+  std::unordered_map<std::string, MetadataSection> optionalSections() const {
+    return optionalSections_;
+  }
+
   std::optional<Section> loadOptionalSection(
       const std::string& name,
       bool keepCache = false) const;
@@ -349,10 +354,7 @@ class TabletReader {
   uint32_t stripeCount_{0};
   const uint32_t* stripeRowCounts_{nullptr};
   const uint64_t* stripeOffsets_{nullptr};
-  std::unordered_map<
-      std::string,
-      std::tuple<uint64_t, uint32_t, CompressionType>>
-      optionalSections_;
+  std::unordered_map<std::string, MetadataSection> optionalSections_;
   mutable folly::Synchronized<
       std::unordered_map<std::string, std::unique_ptr<MetadataBuffer>>>
       optionalSectionsCache_;

dwio/nimble/tablet/tests/TabletTests.cpp

@@ -561,6 +561,11 @@ TEST(TabletTests, OptionalSections) {
         file, useChaniedBuffers);
     nimble::TabletReader tablet{*pool, &readFile};
 
+    ASSERT_EQ(tablet.optionalSections().size(), 3);
+    ASSERT_TRUE(tablet.optionalSections().contains("section1"));
+    ASSERT_TRUE(tablet.optionalSections().contains("section2"));
+    ASSERT_TRUE(tablet.optionalSections().contains("section3"));
+
     auto check1 = [&]() {
       auto section = tablet.loadOptionalSection("section1");
       ASSERT_TRUE(section.has_value());
@@ -607,6 +612,8 @@ TEST(TabletTests, OptionalSectionsEmpty) {
         file, useChaniedBuffers);
     nimble::TabletReader tablet{*pool, &readFile};
 
+    ASSERT_TRUE(tablet.optionalSections().empty());
+
     auto section = tablet.loadOptionalSection("section1");
     ASSERT_FALSE(section.has_value());
   }