Overview

This PR addresses issue #X by migrating the CompilationDatabase from individual JSON files to a single SQLite database per module, significantly improving scalability and reducing filesystem overhead.

Problem

Previously, the compilation database stored compilation state for each source file in separate JSON files:

.ebuild/{moduleName}/compdb/{sourceFile}-{hash}.compile.json

This approach had several limitations:

• Created hundreds of small JSON files for large projects
• Increased filesystem overhead with many file operations
• Made cleanup more complex
• Limited query and transaction capabilities

Solution

Implemented a SQLite-based compilation database with the following structure:

.ebuild/{moduleName}/compilation.db

All source files for a module now share a single SQLite database with the following schema:

CREATE TABLE compilation_entries (
    source_file TEXT PRIMARY KEY,
    output_file TEXT NOT NULL,
    last_compiled TEXT NOT NULL,
    definitions TEXT NOT NULL,
    include_paths TEXT NOT NULL,
    force_includes TEXT NOT NULL,
    dependencies TEXT NOT NULL
)

Key Features

• Single database per module: All source files stored in one SQLite database
• Thread-safe operations: Parameterized queries with proper locking
• Efficient serialization: Base64 encoding for list fields to avoid delimiter conflicts
• Graceful error handling: Database operations fail silently to avoid breaking builds
• Backward compatible: Old JSON files are no longer used but not automatically deleted

Changes Made

1. Added dependency: Microsoft.Data.Sqlite version 9.0.9
2. Updated CompilationDatabase.cs:
   • Replaced JSON serialization with SQLite operations
   • Added database initialization and schema creation
   • Implemented SQL-based CRUD operations
   • Added helper methods for list serialization/deserialization
3. Updated tests:
   • Modified corrupted file test to handle SQLite databases
   • Added test verifying multiple source files share the same database

Benefits

• ✅ Reduced filesystem overhead: One database file instead of hundreds of JSON files
• ✅ Better scalability: Handles large projects with many source files efficiently
• ✅ Atomic operations: SQLite transactions ensure data consistency
• ✅ Improved concurrency: Better handling of concurrent access
• ✅ Simpler management: Single file to backup, cleanup, or inspect

Testing

• All 11 CompilationDatabase unit tests pass (added 1 new test)
• Manual verification confirms database creation and incremental builds work correctly
• Verified compilation skipping behavior functions as expected
• No regressions in existing functionality

Example Usage

After building a module, the SQLite database can be inspected:

$ sqlite3 .ebuild/MyModule/compilation.db "SELECT source_file, output_file FROM compilation_entries;"
/path/to/main.cpp|/path/to/main.o
/path/to/utils.cpp|/path/to/utils.o

The database automatically tracks compilation state for incremental builds, allowing the build system to skip recompilation when source files and their dependencies are unchanged.

Migration Notes

• Existing JSON files in .ebuild/{moduleName}/compdb/ are no longer used
• Users can manually delete the old compdb directories if desired
• The new database is created automatically on first build

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