feat(storage): Write-Optimized Merge (WOM) Tree — v1.8.0

.github/workflows/wom-tree-ci.yml

@@ -0,0 +1,136 @@
+name: Write-Optimized Merge (WOM) Tree CI
+
+# Triggered on every push/PR that touches WomTree sources, tests, or this
+# workflow.  Targets v1.8.0.
+on:
+  push:
+    branches:
+      - main
+      - develop
+    paths:
+      - 'include/storage/wom_tree.h'
+      - 'src/storage/wom_tree.cpp'
+      - 'tests/test_wom_tree.cpp'
+      - 'tests/CMakeLists.txt'
+      - 'cmake/CMakeLists.txt'
+      - '.github/workflows/wom-tree-ci.yml'
+  pull_request:
+    types: [opened, synchronize, reopened]
+    paths:
+      - 'include/storage/wom_tree.h'
+      - 'src/storage/wom_tree.cpp'
+      - 'tests/test_wom_tree.cpp'
+      - 'tests/CMakeLists.txt'
+      - 'cmake/CMakeLists.txt'
+      - '.github/workflows/wom-tree-ci.yml'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  ci-scope-classifier:
+    permissions:
+      contents: read
+    uses: ./.github/workflows/ci-scope-classifier.yml
+
+  # ---------------------------------------------------------------------------
+  # Build and run the WomTree focused test suite.
+  # Tests cover all acceptance criteria:
+  #   AC-1  Lower write amplification (2-5x vs 10-30x for LSM) – verified
+  #         writeAmplification() < 30.0 after 500 inserts with forced flushes.
+  #   AC-2  Better for update-heavy workloads – overwrite 100 keys, read latest.
+  #   AC-3  Reduced compaction overhead – flush_passes == 0 with large buffer;
+  #         compact() flushes lazily buffered ops without data loss.
+  #   AC-4  Higher space amplification – user_bytes_written / internal stats
+  #         exposed and non-zero.
+  #   AC-5  Slower point reads (multi-level traversal) – tree_height > 1 for
+  #         64 entries with leaf_capacity=4; reads still return correct values.
+  # ---------------------------------------------------------------------------
+  wom-tree-unit-tests:
+    needs: ci-scope-classifier
+    if: needs.ci-scope-classifier.outputs.has_code_changes == 'true'
+    name: WOM Tree tests (${{ matrix.os }} / ${{ matrix.compiler }})
+    runs-on: ${{ matrix.os }}
+    permissions:
+      contents: read
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-22.04
+            compiler: gcc-12
+            cc: gcc-12
+            cxx: g++-12
+          - os: ubuntu-22.04
+            compiler: clang-15
+            cc: clang-15
+            cxx: clang++-15
+          - os: ubuntu-24.04
+            compiler: gcc-13
+            cc: gcc-13
+            cxx: g++-13
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Set up C++ build environment
+        uses: ./.github/actions/setup-cpp-build
+        with:
+          cc:             ${{ matrix.cc }}
+          cxx:            ${{ matrix.cxx }}
+          extra-packages: nlohmann-json3-dev libssl-dev libzstd-dev
+
+      - name: Configure (WOM Tree focused test target)
+        env:
+          CC:  ${{ matrix.cc }}
+          CXX: ${{ matrix.cxx }}
+        run: |
+          cmake -B build -G Ninja \
+            -DCMAKE_BUILD_TYPE=Debug \
+            -DCMAKE_C_COMPILER=${{ matrix.cc }} \
+            -DCMAKE_CXX_COMPILER=${{ matrix.cxx }} \
+            -DTHEMIS_ENABLE_LLM=OFF \
+            -DTHEMIS_ENABLE_GPU=OFF
+
+      - name: Build focused test binary
+        run: cmake --build build --target test_wom_tree_focused -- -j$(nproc)
+
+      - name: Run WOM Tree unit tests
+        run: |
+          cd build
+          ctest --test-dir . \
+            --tests-regex WomTreeFocusedTests \
+            --output-on-failure \
+            --timeout 60 \
+            2>&1 | tee wom_tree_test_output.txt
+
+      - name: Upload test results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: wom-tree-results-${{ matrix.os }}-${{ matrix.compiler }}
+          path: |
+            build/wom_tree_test_output.txt
+          retention-days: 14
+
+      - name: Write job summary
+        if: always()
+        run: |
+          echo "## 🌲 Write-Optimized Merge (WOM) Tree – Unit Tests" >> "$GITHUB_STEP_SUMMARY"
+          echo "" >> "$GITHUB_STEP_SUMMARY"
+          echo "| Parameter | Value |" >> "$GITHUB_STEP_SUMMARY"
+          echo "|-----------|-------|" >> "$GITHUB_STEP_SUMMARY"
+          echo "| **OS** | \`${{ matrix.os }}\` |" >> "$GITHUB_STEP_SUMMARY"
+          echo "| **Compiler** | \`${{ matrix.compiler }}\` |" >> "$GITHUB_STEP_SUMMARY"
+          echo "| **Event** | \`${{ github.event_name }}\` |" >> "$GITHUB_STEP_SUMMARY"
+          echo "| **Branch** | \`${{ github.ref_name }}\` |" >> "$GITHUB_STEP_SUMMARY"
+          echo "| **Commit** | \`${{ github.sha }}\` |" >> "$GITHUB_STEP_SUMMARY"
+          echo "| **Triggered by** | ${{ github.actor }} |" >> "$GITHUB_STEP_SUMMARY"
+          echo "" >> "$GITHUB_STEP_SUMMARY"
+          echo "WomTree: Bε-tree write-optimized storage alternative to LSM. Write amplification 2-5× vs 10-30× for LSM. Lazy buffer propagation with reduced compaction overhead." >> "$GITHUB_STEP_SUMMARY"

cmake/CMakeLists.txt

@@ -1441,6 +1441,7 @@ set(THEMIS_CORE_SOURCES
     ../src/storage/transaction_retry_manager.cpp
     ../src/storage/compaction_manager.cpp
     ../src/storage/merge_operators.cpp
+    ../src/storage/wom_tree.cpp
     ../src/storage/compressed_storage.cpp
     ../src/storage/compression_strategy.cpp
     ../src/storage/gpu_compression.cpp