Add a relaxed durability mode for use with the idb vfs (#79)

* Add a relaxed durability for use with the idb vfs

* Update readme

packages/pglite/README.md

@@ -152,6 +152,7 @@ Path to the directory to store the Postgres database. You can provide a url sche
 ##### `options`:
 
 - `debug`: 1-5 - the Postgres debug level. Logs are sent to the console.
+- `relaxedDurability`: boolean - under relaxed durability mode PGlite will not wait for flushes to storage to complete when using the indexedDB file system.
 
 ### Methods:
 

packages/pglite/src/interface.ts

@@ -21,6 +21,7 @@ export interface ExecProtocolOptions {
 
 export interface PGliteOptions {
   debug?: DebugLevel;
+  relaxedDurability?: boolean;
 }
 
 export interface PGliteInterface {

packages/pglite/src/pglite.ts

@@ -38,6 +38,7 @@ export class PGlite implements PGliteInterface {
   #closing = false;
   #closed = false;
   #inTransaction = false;
+  #relaxedDurability = false;
 
   #resultAccumulator: Uint8Array[] = [];
 
@@ -47,6 +48,7 @@ export class PGlite implements PGliteInterface {
   #queryMutex = new Mutex();
   #transactionMutex = new Mutex();
   #fsSyncMutex = new Mutex();
+  #fsSyncScheduled = false;
 
   readonly debug: DebugLevel = 0;
 
@@ -69,6 +71,11 @@ export class PGlite implements PGliteInterface {
       this.debug = options.debug;
     }
 
+    // Enable relaxed durability if requested
+    if (options?.relaxedDurability !== undefined) {
+      this.#relaxedDurability = options.relaxedDurability;
+    }
+
     // Create an event target to handle events from the emscripten module
     this.#eventTarget = new EventTarget();
 
@@ -474,8 +481,22 @@ export class PGlite implements PGliteInterface {
    * run after every query to ensure that the filesystem is synced.
    */
   async #syncToFs() {
-    await this.#fsSyncMutex.runExclusive(async () => {
-      await this.fs!.syncToFs(this.emp.FS);
-    });
+    if (this.#fsSyncScheduled) {
+      return;
+    }
+    this.#fsSyncScheduled = true;
+
+    const doSync = async () => {
+      await this.#fsSyncMutex.runExclusive(async () => {
+        this.#fsSyncScheduled = false;
+        await this.fs!.syncToFs(this.emp.FS);
+      });
+    };
+
+    if (this.#relaxedDurability) {
+      doSync();
+    } else {
+      await doSync();
+    }
   }
 }

packages/pglite/src/worker/index.ts

@@ -23,11 +23,13 @@ export class PGliteWorker implements PGliteInterface {
   #closed = false;
 
   #worker: WorkerInterface;
+  #options: PGliteOptions;
 
   constructor(dataDir: string, options?: PGliteOptions) {
     const { dataDir: dir, fsType } = parseDataDir(dataDir);
     this.dataDir = dir;
     this.fsType = fsType;
+    this.#options = options ?? {};
     this.debug = options?.debug ?? 0;
 
     this.#worker = Comlink.wrap(new Worker(WORKER_URL, { type: "module" }));
@@ -37,7 +39,7 @@ export class PGliteWorker implements PGliteInterface {
   }
 
   async #init(dataDir: string) {
-    await this.#worker.init(dataDir, { debug: this.debug });
+    await this.#worker.init(dataDir, this.#options);
     this.#ready = true;
   }