SQL: Batch save, using transactions

app/logic/Mail/IMAP/IMAPFolder.ts

@@ -373,29 +373,15 @@ export class IMAPFolder extends Folder {
 
   /** Save headers of newly discovered emails */
   protected async saveNewMsgs(msgs: Collection<IMAPEMail>) {
-    // Saving message headers is so slow and expensive
-    // that it drags down the whole app.
-    // It's far faster to re-download the headers from the server.
-    // Disable it for now, until we can save faster, e.g. as batches.
+    // Saving message headers is slow and expensive,
+    // and it drags down the whole app.
+    // It's faster to re-download the headers from the server.
+    // Disable saving only message headers for now.
     // We will still save the completely downloaded emails, in
     // `downloadMessages()` -> `msg.saveCompleteMessage()`
     return;
-    await this.saveNewMsgsDirectly(msgs);
-    this.saveNewMsgsDirectly(msgs)
-      .catch(this.account.errorCallback);
-  }
-
-  protected async saveNewMsgsDirectly(msgs: Collection<IMAPEMail>) {
     let startTime = Date.now();
-    for (let email of msgs) {
-      try {
-        if (email.subject) {
-          await this.storage.saveMessage(email);
-        }
-      } catch (ex) {
-        this.account.errorCallback(ex);
-      }
-    }
+    await this.storage.saveMessages(msgs);
     let saveTime = Date.now() - startTime;
     console.log("  Saved", msgs.length, "msgs in", saveTime, "ms =", saveTime / msgs.length, "ms/msg");
   }

app/logic/Mail/MailAccount.ts

@@ -208,6 +208,7 @@ export interface MailAccountStorage {
   readMessageWritableProps(email: EMail): Promise<void>;
   readMessageBody(email: EMail): Promise<void>;
   saveMessage(email: EMail): Promise<void>;
+  saveMessages(emails: Collection<EMail>): Promise<void>;
   saveMessageWritableProps(email: EMail): Promise<void>;
   saveMessageTags(email: EMail): Promise<void>;
   deleteMessage(email: EMail): Promise<void>;

app/logic/Mail/SQL/SQLEMail.ts

@@ -5,9 +5,10 @@ import { Attachment, ContentDisposition } from "../Attachment";
 import { getTagByName, Tag } from "../Tag";
 import { JSONEMail } from "../JSON/JSONEMail";
 import { getDatabase } from "./SQLDatabase";
-import { assert, fileExtensionForMIMEType } from "../../util/util";
-import { ArrayColl } from "svelte-collections";
 import { sanitize } from "../../../../lib/util/sanitizeDatatypes";
+import { Lock } from "../../util/Lock";
+import { assert, fileExtensionForMIMEType } from "../../util/util";
+import { ArrayColl, Collection } from "svelte-collections";
 import sql from "../../../../lib/rs-sqlite";
 
 export class SQLEMail {
@@ -212,6 +213,25 @@ export class SQLEMail {
       )`);
   }
 
+  protected static transactionLock = new Lock();
+
+  static async saveMultiple(emails: Collection<EMail>) {
+    let lock = await this.transactionLock.lock();
+    try {
+      await (await getDatabase()).run(sql`BEGIN TRANSACTION`);
+      for (let email of emails) {
+        if (!email.subject) {
+          continue;
+        }
+        await this.save(email);
+      }
+      await (await getDatabase()).run(sql`END TRANSACTION`);
+    } finally {
+      lock.release();
+    }
+  }
+
+
   static async read(dbID: number, email: EMail, row?: any, recipientRows?: any[], attachmentRows?: any[], tagRows?: any[]): Promise<EMail> {
     if (!row) {
       // <copied to="readAll()" />

app/logic/Mail/SQL/SQLMailStorage.ts

@@ -5,7 +5,6 @@ import { SQLEMail } from "./SQLEMail";
 import type { Folder } from "../Folder";
 import { SQLFolder } from "./SQLFolder";
 import type { Collection } from "svelte-collections";
-import { backgroundError } from "../../../frontend/Util/error";
 
 export class SQLMailStorage implements MailAccountStorage {
   async saveAccount(account: MailAccount): Promise<void> {
@@ -46,6 +45,9 @@ export class SQLMailStorage implements MailAccountStorage {
   async saveMessage(email: EMail): Promise<void> {
     await SQLEMail.save(email);
   }
+  async saveMessages(emails: Collection<EMail>): Promise<void> {
+    await SQLEMail.saveMultiple(emails);
+  }
   async saveMessageWritableProps(email: EMail): Promise<void> {
     await SQLEMail.saveWritableProps(email);
   }