add cachebusting

Author: bakkot

README.md

@@ -77,6 +77,12 @@ const result = await worker.db.exec(`select * from table where id = ?`, [123]);
 
 ```
 
+## Cachebusting
+
+Alongside the `url` or `urlPrefix`, config can take an optional `cacheBust` property whose value will be appended as a query parameter to URLs. If you set it to a random value when you update the database you can avoid caching-related database corruption.
+
+If using a remote config (`from: 'jsonconfig'`), don't forget to cachebust that too.
+
 ## Debugging data fetching
 
 If your query is fetching a lot of data and you're not sure why, try this:

src/sqlite.worker.ts

@@ -59,6 +59,7 @@ export type SplitFileConfigPure = {
 };
 export type SplitFileConfigInner = {
   requestChunkSize: number;
+  cacheBust?: string;
 } & (
   | {
       serverMode: "chunked";
@@ -145,20 +146,21 @@ const mod = {
         config.serverMode === "chunked" ? config.urlPrefix : config.url;
       console.log("constructing url database", id);
       let rangeMapper: RangeMapper;
+      let suffix = config.cacheBust ? "?cb=" + config.cacheBust : "";
       if (config.serverMode == "chunked") {
         rangeMapper = (from: number, to: number) => {
           const serverChunkId = (from / config.serverChunkSize) | 0;
           const serverFrom = from % config.serverChunkSize;
           const serverTo = serverFrom + (to - from);
           return {
-            url: config.urlPrefix + String(serverChunkId).padStart(3, "0"),
+            url: config.urlPrefix + String(serverChunkId).padStart(3, "0") + suffix,
             fromByte: serverFrom,
             toByte: serverTo,
           };
         };
       } else {
         rangeMapper = (fromByte, toByte) => ({
-          url: config.url,
+          url: config.url + suffix,
           fromByte,
           toByte,
         });