Merge branch 'jjlin-db-conn-init' into main

.env.template

@@ -29,6 +29,15 @@
 ## Define the size of the connection pool used for connecting to the database.
 # DATABASE_MAX_CONNS=10
 
+## Database connection initialization
+## Allows SQL statements to be run whenever a new database connection is created.
+## This is mainly useful for connection-scoped pragmas.
+## If empty, a database-specific default is used:
+## - SQLite: "PRAGMA busy_timeout = 5000; PRAGMA synchronous = NORMAL;"
+## - MySQL: ""
+## - PostgreSQL: ""
+# DATABASE_CONN_INIT=""
+
 ## Individual folders, these override %DATA_FOLDER%
 # RSA_KEY_FILENAME=data/rsa_key
 # ICON_CACHE_FOLDER=data/icon_cache

src/config.rs

@@ -520,6 +520,9 @@ make_config! {
         /// Database connection pool size
         database_max_conns:     u32,    false,  def,    10;
 
+        /// Database connection init |> SQL statements to run when creating a new database connection, mainly useful for connection-scoped pragmas. If empty, a database-specific default is used.
+        database_conn_init:     String, false,  def,    "".to_string();
+
         /// Bypass admin page security (Know the risks!) |> Disables the Admin Token for the admin page so you may use your own auth in-front
         disable_admin_token:    bool,   true,   def,    false;
 

src/db/mod.rs

@@ -1,6 +1,10 @@
 use std::{sync::Arc, time::Duration};
 
-use diesel::r2d2::{ConnectionManager, Pool, PooledConnection};
+use diesel::{
+    connection::SimpleConnection,
+    r2d2::{ConnectionManager, CustomizeConnection, Pool, PooledConnection},
+};
+
 use rocket::{
     http::Status,
     outcome::IntoOutcome,
@@ -62,6 +66,23 @@ macro_rules! generate_connections {
         #[allow(non_camel_case_types)]
         pub enum DbConnInner { $( #[cfg($name)] $name(PooledConnection<ConnectionManager< $ty >>), )+ }
 
+        #[derive(Debug)]
+        pub struct DbConnOptions {
+            pub init_stmts: String,
+        }
+
+        $( // Based on <https://stackoverflow.com/a/57717533>.
+        #[cfg($name)]
+        impl CustomizeConnection<$ty, diesel::r2d2::Error> for DbConnOptions {
+            fn on_acquire(&self, conn: &mut $ty) -> Result<(), diesel::r2d2::Error> {
+                (|| {
+                    if !self.init_stmts.is_empty() {
+                        conn.batch_execute(&self.init_stmts)?;
+                    }
+                    Ok(())
+                })().map_err(diesel::r2d2::Error::QueryError)
+            }
+        })+
 
         #[derive(Clone)]
         pub struct DbPool {
@@ -103,7 +124,8 @@ macro_rules! generate_connections {
         }
 
         impl DbPool {
-            // For the given database URL, guess it's type, run migrations create pool and return it
+            // For the given database URL, guess its type, run migrations, create pool, and return it
+            #[allow(clippy::diverging_sub_expression)]
             pub fn from_config() -> Result<Self, Error> {
                 let url = CONFIG.database_url();
                 let conn_type = DbConnType::from_url(&url)?;
@@ -117,6 +139,9 @@ macro_rules! generate_connections {
                             let pool = Pool::builder()
                                 .max_size(CONFIG.database_max_conns())
                                 .connection_timeout(Duration::from_secs(CONFIG.database_timeout()))
+                                .connection_customizer(Box::new(DbConnOptions{
+                                    init_stmts: conn_type.get_init_stmts()
+                                }))
                                 .build(manager)
                                 .map_res("Failed to create pool")?;
                             return Ok(DbPool {
@@ -190,6 +215,23 @@ impl DbConnType {
             err!("`DATABASE_URL` looks like a SQLite URL, but 'sqlite' feature is not enabled")
         }
     }
+
+    pub fn get_init_stmts(&self) -> String {
+        let init_stmts = CONFIG.database_conn_init();
+        if !init_stmts.is_empty() {
+            init_stmts
+        } else {
+            self.default_init_stmts()
+        }
+    }
+
+    pub fn default_init_stmts(&self) -> String {
+        match self {
+            Self::sqlite => "PRAGMA busy_timeout = 5000; PRAGMA synchronous = NORMAL;".to_string(),
+            Self::mysql => "".to_string(),
+            Self::postgresql => "".to_string(),
+        }
+    }
 }
 
 #[macro_export]