Module backends 

Concrete storage backend implementations for the incremental update system.

This module provides database-specific implementations of the StorageBackend trait:

• Postgres (postgres-backend feature): Full SQL backend for CLI deployment with connection pooling, prepared statements, and batch operations.
• D1 (d1-backend feature): Cloudflare D1 backend for edge deployment via the Cloudflare REST API.
• InMemory: Simple in-memory backend for testing (always available).

Backend Factory Pattern

The create_backend factory function provides runtime backend selection based on deployment environment and feature flags:

use thread_flow::incremental::backends::{BackendType, BackendConfig, create_backend};

// CLI deployment with Postgres
let backend = create_backend(
    BackendType::Postgres,
    BackendConfig::Postgres {
        database_url: "postgresql://localhost/thread".to_string(),
    },
).await?;

// Edge deployment with D1
let backend = create_backend(
    BackendType::D1,
    BackendConfig::D1 {
        account_id: "your-account-id".to_string(),
        database_id: "your-db-id".to_string(),
        api_token: "your-token".to_string(),
    },
).await?;

// Testing with in-memory storage (always available)
let backend = create_backend(
    BackendType::InMemory,
    BackendConfig::InMemory,
).await?;

Feature Gating

Backend availability depends on cargo features:

• postgres-backend: Enables PostgresIncrementalBackend
• d1-backend: Enables [D1IncrementalBackend]
• No features required: InMemoryStorage always available

Attempting to use a disabled backend returns IncrementalError::UnsupportedBackend.

Deployment Scenarios

CLI Deployment (Postgres)

[dependencies]
thread-flow = { version = "*", features = ["postgres-backend"] }

use thread_flow::incremental::backends::{BackendType, BackendConfig, create_backend};

let backend = create_backend(
    BackendType::Postgres,
    BackendConfig::Postgres {
        database_url: std::env::var("DATABASE_URL")?,
    },
).await?;

Edge Deployment (D1)

[dependencies]
thread-flow = { version = "*", features = ["d1-backend", "worker"] }

use thread_flow::incremental::backends::{BackendType, BackendConfig, create_backend};

let backend = create_backend(
    BackendType::D1,
    BackendConfig::D1 {
        account_id: std::env::var("CF_ACCOUNT_ID")?,
        database_id: std::env::var("CF_DATABASE_ID")?,
        api_token: std::env::var("CF_API_TOKEN")?,
    },
).await?;

Testing (InMemory)

use thread_flow::incremental::backends::{BackendType, BackendConfig, create_backend};

let backend = create_backend(
    BackendType::InMemory,
    BackendConfig::InMemory,
).await?;

Re-exports

pub use postgres::PostgresIncrementalBackend;

Modules

postgres

PostgreSQL storage backend for the incremental update system.

Enums

BackendConfig

Configuration for backend initialization.

BackendType

Backend type selector for runtime backend selection.

IncrementalError

Errors that can occur during backend initialization and operation.

Functions

create_backend

Creates a storage backend based on the specified type and configuration.