Add support for serialized threading mode to sqlite (#1514)

* Add support for serialized threading mode

* Typos

* Fix build

sqlx-core/src/sqlite/connection/establish.rs

@@ -7,8 +7,8 @@ use crate::{
 };
 use libsqlite3_sys::{
     sqlite3_busy_timeout, sqlite3_extended_result_codes, sqlite3_open_v2, SQLITE_OK,
-    SQLITE_OPEN_CREATE, SQLITE_OPEN_MEMORY, SQLITE_OPEN_NOMUTEX, SQLITE_OPEN_PRIVATECACHE,
-    SQLITE_OPEN_READONLY, SQLITE_OPEN_READWRITE, SQLITE_OPEN_SHAREDCACHE,
+    SQLITE_OPEN_CREATE, SQLITE_OPEN_FULLMUTEX, SQLITE_OPEN_MEMORY, SQLITE_OPEN_NOMUTEX,
+    SQLITE_OPEN_PRIVATECACHE, SQLITE_OPEN_READONLY, SQLITE_OPEN_READWRITE, SQLITE_OPEN_SHAREDCACHE,
 };
 use sqlx_rt::blocking;
 use std::io;
@@ -33,7 +33,11 @@ pub(crate) async fn establish(options: &SqliteConnectOptions) -> Result<SqliteCo
     // [SQLITE_OPEN_NOMUTEX] will instruct [sqlite3_open_v2] to return an error if it
     // cannot satisfy our wish for a thread-safe, lock-free connection object
 
-    let mut flags = SQLITE_OPEN_NOMUTEX;
+    let mut flags = if options.serialized {
+        SQLITE_OPEN_FULLMUTEX
+    } else {
+        SQLITE_OPEN_NOMUTEX
+    };
 
     flags |= if options.read_only {
         SQLITE_OPEN_READONLY

sqlx-core/src/sqlite/options/mod.rs

@@ -61,6 +61,7 @@ pub struct SqliteConnectOptions {
     pub(crate) log_settings: LogSettings,
     pub(crate) immutable: bool,
     pub(crate) pragmas: IndexMap<Cow<'static, str>, Cow<'static, str>>,
+    pub(crate) serialized: bool,
 }
 
 impl Default for SqliteConnectOptions {
@@ -109,6 +110,7 @@ impl SqliteConnectOptions {
             log_settings: Default::default(),
             immutable: false,
             pragmas,
+            serialized: false,
         }
     }
 
@@ -234,4 +236,14 @@ impl SqliteConnectOptions {
         self.immutable = immutable;
         self
     }
+
+    /// Sets the [threading mode](https://www.sqlite.org/threadsafe.html) for the database connection.
+    ///
+    /// The default setting is `false` corersponding to using `OPEN_NOMUTEX`, if `true` then `OPEN_FULLMUTEX`.
+    ///
+    /// See [open](https://www.sqlite.org/c3ref/open.html) for more details.
+    pub fn serialized(mut self, serialized: bool) -> Self {
+        self.serialized = serialized;
+        self
+    }
 }