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Database Abstraction Layer (DAL) & fb-cpp Migration

This document describes the architectural changes introduced during the migration from the legacy IBPP library to the modern fb-cpp wrapper.

Overview

The migration follows a "heart transplant" strategy, introducing a backend-agnostic abstraction layer that allows FlameRobin to support both the legacy IBPP library and the modern fb-cpp wrapper simultaneously during the transition.

Architectural Diagram

graph TD
    subgraph "Application Layer"
        Metadata[Metadata Classes: Database/Server]
    end

    subgraph "Database Abstraction Layer (DAL)"
        Factory[DatabaseFactory]
        subgraph "Interfaces (C++20)"
            IDB[IDatabase]
            ITX[ITransaction]
            IST[IStatement]
            ISV[IService]
        end
    end

    subgraph "Backends"
        direction LR
        subgraph "Legacy"
            IBPP_Impl[IBPP Implementation]
            IBPP_Lib[(IBPP Library)]
        end

        subgraph "Modern"
            FBCPP_Impl[fb-cpp Implementation]
            FBCPP_Lib[(fb-cpp Submodule)]
        end
    end

    %% Relationships
    Metadata -->|Uses| Factory
    Factory -->|Instantiates| IDB
    IDB -.-> IBPP_Impl
    IDB -.-> FBCPP_Impl
    
    IBPP_Impl --> IBPP_Lib
    FBCPP_Impl --> FBCPP_Lib

    %% Styling
    style FBCPP_Impl fill:#f9f,stroke:#333,stroke-width:2px
    style IDB fill:#bbf,stroke:#333,stroke-width:2px
    style ITX fill:#bbf,stroke:#333,stroke-width:2px
    style IST fill:#bbf,stroke:#333,stroke-width:2px
    style ISV fill:#bbf,stroke:#333,stroke-width:2px
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Migration Components

Abstract Interfaces (src/engine/db/)

  • IDatabase: Manages database connections and lifecycle.
  • ITransaction: Handles transaction boundaries and isolation levels.
  • IStatement: Encapsulates SQL preparation, execution, parameter binding, and result set fetching.
  • IService: Provides access to Firebird services (backup, restore, maintenance).

Database Factory

The DatabaseFactory class manages the instantiation of the appropriate backend based on configuration or runtime requirements.

Backends

  1. IBPP Backend: A complete implementation of the DAL interfaces using the existing IBPP library, ensuring no regression during migration.
  2. fb-cpp Backend: A modern implementation leveraging C++20 and the latest Firebird API features.

Discussion Summary (from PR #543)

  • Modernization: The project has been upgraded to C++20 to support the new abstraction layer and the fb-cpp library.
  • Dependency Management: vcpkg is now used for dependency management, including a custom registry for Firebird-related components.
  • Incremental Refactoring: Metadata classes are being updated to hold pointers to DAL interfaces rather than direct IBPP objects, allowing for a gradual transition.
  • Build System: CMake has been enhanced to handle cross-platform discovery of Firebird and wxWidgets via vcpkg.