feedsignal/crates/db/src/lib.rs

mod affinities;
mod articles;
mod feeds;
mod models;
mod reading_events;

pub use models::RankedArticleRow;
pub(crate) mod schema;

use anyhow::Result;
use diesel::prelude::*;
use diesel::sqlite::SqliteConnection;
use diesel_async::pooled_connection::bb8::Pool;
use diesel_async::pooled_connection::AsyncDieselConnectionManager;
use diesel_async::sync_connection_wrapper::SyncConnectionWrapper;
use diesel_migrations::{embed_migrations, EmbeddedMigrations, MigrationHarness};

const MIGRATIONS: EmbeddedMigrations = embed_migrations!("./migrations");

/// SQLite has no native async driver, so `diesel-async` wraps a blocking
/// `SqliteConnection` and runs it on a blocking thread under the hood.
type AsyncSqliteConnection = SyncConnectionWrapper<SqliteConnection>;

#[derive(Clone)]
pub struct Db {
    pool: Pool<AsyncSqliteConnection>,
}

impl Db {
    /// `database_url` is a plain SQLite file path (e.g. "feedsignal.db"),
    /// created if it doesn't exist. Everything lives in one file, no
    /// separate database server to run.
    pub async fn connect(database_url: &str) -> Result<Self> {
        // `MigrationHarness` only works on a synchronous `Connection`, and
        // this only runs once at boot, so open a throwaway sync connection
        // just for it rather than pulling migrations through the async pool.
        // Each pending migration runs in its own transaction (SQLite
        // supports transactional DDL), and `down.sql` gives each one a
        // matching revert.
        let url = database_url.to_string();
        tokio::task::spawn_blocking(move || -> Result<()> {
            let mut conn = SqliteConnection::establish(&url)?;
            conn.run_pending_migrations(MIGRATIONS)
                .map_err(|e| anyhow::anyhow!(e))?;
            Ok(())
        })
        .await??;

        let manager = AsyncDieselConnectionManager::<AsyncSqliteConnection>::new(database_url);
        let pool = Pool::builder().max_size(5).build(manager).await?;
        Ok(Self { pool })
    }
}