Add new database driver creation instructions to the contributing.md file

CONTRIBUTING.md

@@ -37,6 +37,214 @@ To start with, check out:
 
 Additionally, it's always good to work on improving/adding examples and documentation.
 
+## Adding Support for New Databases
+
+Adding support for a new database to SQLx is a significant undertaking that requires implementing multiple traits and components. This guide provides a step-by-step approach to building a database driver progressively, with testing at each stage.
+
+### Overview of SQLx Architecture
+
+SQLx uses a trait-based architecture where each database implements a set of core traits:
+
+- **[`Database`](sqlx-core/src/database.rs)**: The main trait that defines all associated types for a database. This is the central trait that ties everything together and must be implemented for your database struct.
+
+- **[`Connection`](sqlx-core/src/connection.rs)**: Handles database connections and basic operations like connecting, closing, pinging, and transaction management. See examples: [PostgreSQL](sqlx-core/src/postgres/connection/mod.rs), [MySQL](sqlx-core/src/mysql/connection/mod.rs), [SQLite](sqlx-core/src/sqlite/connection/mod.rs).
+
+- **[`Row`](sqlx-core/src/row.rs)**: Represents a single row from a query result, providing access to column data by index or name. Examples: [PgRow](sqlx-core/src/postgres/row.rs), [MySqlRow](sqlx-core/src/mysql/row.rs).
+
+- **[`Column`](sqlx-core/src/column.rs)**: Provides metadata about columns (name, type, etc.). Examples: [PgColumn](sqlx-core/src/postgres/column.rs), [MySqlColumn](sqlx-core/src/mysql/column.rs).
+
+- **[`Value`](sqlx-core/src/value.rs) and [`ValueRef`](sqlx-core/src/value.rs)**: Handle owned and borrowed values from the database. Examples: [PgValue](sqlx-core/src/postgres/value.rs), [MySqlValue](sqlx-core/src/mysql/value.rs).
+
+- **[`TypeInfo`](sqlx-core/src/type_info.rs)**: Provides information about database types for the type system. Examples: [PgTypeInfo](sqlx-core/src/postgres/type_info.rs), [MySqlTypeInfo](sqlx-core/src/mysql/type_info.rs).
+
+- **[`Arguments`](sqlx-core/src/arguments.rs)**: Handles query parameter binding and encoding. Examples: [PgArguments](sqlx-core/src/postgres/arguments.rs), [MySqlArguments](sqlx-core/src/mysql/arguments.rs).
+
+- **[`Statement`](sqlx-core/src/statement.rs)**: Handles prepared statements and their metadata. Examples: [PgStatement](sqlx-core/src/postgres/statement.rs), [MySqlStatement](sqlx-core/src/mysql/statement.rs).
+
+- **Query execution**: Implement [`Executor`](sqlx-core/src/executor.rs) for your connection type to handle query execution and result streaming.
+
+### Prerequisites
+
+Before starting, ensure you have:
+1. A working database server/client library to connect to your database
+2. Understanding of your database's wire protocol or client API
+3. Knowledge of your database's type system and SQL dialect
+
+### Step 1: Initial Setup and Feature Configuration
+
+**1.1 Add feature flags to Cargo.toml files:**
+
+Add your database feature to the main `Cargo.toml`, `sqlx-core/Cargo.toml`, and `sqlx-macros/Cargo.toml`. Follow the pattern used by existing databases like `postgres` or `mysql`. Include any native client library dependencies as optional dependencies.
+
+**1.2 Create the basic module structure:**
+```bash
+mkdir -p sqlx-core/src/yourdb
+```
+
+**1.3 Add the module to `sqlx-core/src/lib.rs` and main `src/lib.rs`** with appropriate feature gates.
+
+**Test:** `cargo check --features yourdb`
+
+### Step 2: Database Struct and Core Types
+
+**2.1 Create your database struct** that will implement the [`Database`](sqlx-core/src/database.rs) trait. Look at [Postgres](sqlx-core/src/postgres/database.rs), [MySQL](sqlx-core/src/mysql/database.rs), or [SQLite](sqlx-core/src/sqlite/database.rs) for examples.
+
+**2.2 Implement core types:**
+- **TypeInfo**: Represents your database's type system. Study existing implementations to understand how to map database types to Rust types.
+- **Value and ValueRef**: Handle data storage and retrieval. These work with your database's binary or text protocol.
+- **DatabaseError**: Convert your database's native errors to SQLx's error system.
+
+**Test:** `cargo check --features yourdb`
+
+### Step 3: Connection Implementation
+
+**3.1 Implement [`Connection`](sqlx-core/src/connection.rs)** for your database. This handles:
+- Connection establishment and URL parsing ([`ConnectOptions`](sqlx-core/src/connection.rs))
+- Connection lifecycle (open, close, ping)
+- Basic connection management
+
+Study the connection implementations in existing drivers, particularly how they handle:
+- Network protocols (see [PostgreSQL stream handling](sqlx-core/src/postgres/connection/stream.rs))
+- Authentication (see [MySQL auth](sqlx-core/src/mysql/connection/auth.rs))
+- Connection options parsing (see [PostgreSQL options](sqlx-core/src/postgres/options/mod.rs))
+
+**Test:** Basic connection establishment
+
+### Step 4: Type System Integration
+
+**4.1 Implement [`Type`](sqlx-core/src/types/mod.rs), [`Encode`](sqlx-core/src/encode.rs), and [`Decode`](sqlx-core/src/decode.rs)** traits for basic Rust types.
+
+Start with simple types like strings and integers. Look at existing type implementations:
+- [PostgreSQL types](sqlx-core/src/postgres/types/)
+- [MySQL types](sqlx-core/src/mysql/types/)
+- [SQLite types](sqlx-core/src/sqlite/types/)
+
+Each type needs:
+- `Type` implementation to provide type metadata
+- `Encode` implementation to convert Rust values to database format
+- `Decode` implementation to convert database values to Rust types
+
+**Test:** Type conversion unit tests
+
+### Step 5: Query Arguments
+
+**5.1 Implement [`Arguments`](sqlx-core/src/arguments.rs)** for your database. This handles parameter binding in prepared statements.
+
+Study how existing databases handle parameter encoding:
+- [PostgreSQL arguments](sqlx-core/src/postgres/arguments.rs) (binary protocol)
+- [MySQL arguments](sqlx-core/src/mysql/arguments.rs) (binary protocol)
+- [SQLite arguments](sqlx-core/src/sqlite/arguments.rs) (uses native SQLite binding)
+
+**Test:** Parameter binding and encoding
+
+### Step 6: Query Execution
+
+**6.1 Implement [`Executor`](sqlx-core/src/executor.rs)** for your connection type. This is where queries are actually sent to the database and results are processed.
+
+Look at executor implementations:
+- [PostgreSQL executor](sqlx-core/src/postgres/connection/executor.rs)
+- [MySQL executor](sqlx-core/src/mysql/connection/executor.rs)
+- [SQLite executor](sqlx-core/src/sqlite/connection/executor.rs)
+
+**6.2 Implement Row, Column, and QueryResult types** to handle query results and metadata.
+
+**Test:** Basic query execution (`SELECT 1`, simple queries)
+
+### Step 7: Statement Preparation
+
+**7.1 Implement [`Statement`](sqlx-core/src/statement.rs)** if your database supports prepared statements.
+
+Study existing statement implementations to understand:
+- Statement preparation and caching
+- Parameter metadata
+- Column metadata
+
+**Test:** Prepared statement execution with parameters
+
+### Step 8: Transaction Management
+
+**8.1 Implement transaction support** by implementing the transaction-related methods in your `Connection` and creating a `TransactionManager`.
+
+Look at existing transaction implementations:
+- [PostgreSQL transactions](sqlx-core/src/postgres/transaction.rs)
+- [MySQL transactions](sqlx-core/src/mysql/transaction.rs)
+
+**Test:** BEGIN, COMMIT, ROLLBACK operations
+
+### Step 9: Integration with Any Driver
+
+**9.1 Add your database to the [`Any`](sqlx-core/src/any/) driver** to support runtime database selection.
+
+This involves:
+- Adding your database to [`AnyKind`](sqlx-core/src/any/kind.rs)
+- Adding connection type to [`AnyConnectionKind`](sqlx-core/src/any/connection/mod.rs)
+- Updating delegation macros in Any implementations
+- Adding to other Any components (arguments, values, etc.)
+
+Study how existing databases are integrated into the Any driver.
+
+**Test:** Runtime database selection with Any driver
+
+### Step 10: CI and Testing Infrastructure
+
+**10.1 Add CI support** by updating `.github/workflows/ci.yml` with:
+- Your database service in GitHub Actions
+- Test job for your database
+- Appropriate environment variables and health checks
+
+**10.2 Create integration tests** in `tests/yourdb/` following the pattern of existing database tests.
+
+**10.3 Add testing utilities** by implementing [`TestSupport`](sqlx-core/src/testing/mod.rs) for your database.
+
+### Step 11: Advanced Features (Optional)
+
+**11.1 Migration support**: Implement [`MigrateDatabase`](sqlx-core/src/migrate/migrate.rs) if your database supports schema migrations.
+
+**11.2 Listen/Notify**: If your database supports real-time notifications, implement listener functionality (see [PostgreSQL listener](sqlx-core/src/postgres/listener.rs)).
+
+**11.3 Additional type support**: Add support for database-specific types, arrays, JSON, etc.
+
+### Step 12: Documentation and Examples
+
+**12.1 Add comprehensive documentation** to all public APIs with examples.
+
+**12.2 Create examples** in `examples/yourdb/` showing common usage patterns.
+
+**12.3 Update the main README** to include your database in the supported databases list.
+
+### Testing Strategy
+
+At each step, create tests that verify:
+
+1. **Compilation**: `cargo check --features yourdb`
+2. **Unit tests**: Test individual components in isolation
+3. **Integration tests**: Test database connectivity and operations  
+4. **Type safety**: Ensure compile-time type checking works
+5. **Runtime behavior**: Test actual database operations
+
+### Implementation Tips
+
+- **Study existing implementations**: The PostgreSQL, MySQL, and SQLite drivers provide excellent examples of different approaches (network protocols vs embedded databases, binary vs text protocols, etc.).
+
+- **Start simple**: Begin with basic string queries before adding prepared statements, transactions, and complex types.
+
+- **Incremental development**: Test each component thoroughly before moving to the next.
+
+- **Protocol efficiency**: Use binary protocols when available for better performance.
+
+- **Error handling**: Provide clear error messages and proper error type conversions.
+
+- **Memory safety**: Pay careful attention to lifetimes, especially in async contexts.
+
+### Common Patterns
+
+- **Module organization**: Follow the established pattern of separate modules for connection, types, arguments, etc.
+- **Feature gating**: Ensure all database-specific code is behind feature flags.
+- **Async patterns**: Use `BoxFuture` for async trait methods and `BoxStream` for result streaming.
+- **Protocol handling**: Implement proper buffering and message framing for network protocols.
+
+This progressive approach ensures you can test and validate each component before moving to the next, making the development process manageable and reducing the likelihood of errors.
+
 ## Communication
 
 If you're unsure about your contribution or simply want to ask a question about anything, you can: