Creating or extending search index is slow

[bedhub]

Describe the bug
Search index creation is very slow even if there are just a few hundred emails in the inbox. I noticed that when trying to find an email in my personal mailbox that is from 8 years ago but it is also slow if i just create the initial mail index for the first 30 days.

To Reproduce
Steps to reproduce the behavior:

1. Login in to desktop or web app.
2. Ensure that no credentials or search index is stored for the account you want to test with (check using dev tools)
3. Enable search and observe log
4. Check search index performance output from IndexerCore.ts

Expected behavior
Search index is created in a few seconds.

Additional context
Here is an example of the initial indexin

30 days, 74 mails, 50670ms

IndexerCore.ts:941 {"indexingTime":57.59999999962747,"storageTime":1480,"preparingTime":49190.19999999739,"mailcount":74,"storedBytes":760928,"encryptionTime":369.199999996461,"writeRequests":5148,"largestColumn":295,"words":5012,"indexedBytes":682158,"downloadingTime":48763.400000001304} total time:  50670.19999999739

Similar results for extending the index for 30 more days.
next 30 days, 61 mails, 58618ms

IndexerCore.ts:941 {"indexingTime":57.599999997764826,"storageTime":1886,"preparingTime":56732.50000000186,"mailcount":61,"storedBytes":649648,"encryptionTime":353.40000000037253,"writeRequests":4285,"largestColumn":413,"words":1989,"indexedBytes":663768,"downloadingTime":56321.500000003725} total time:  58618.50000000186. 

[ganthern]

"preparingTime":56732.50000000186

that's loading the mail (from cache or server)

"downloadingTime":56321.500000003725

that's downloadingTime: this._stats.preparingTime - this._stats.indexingTime - this._stats.encryptionTime

so it's the server? since this happens on the web app and the desktop app and those use different cache implementations (the web app one is always empty on startup). Definitely worth exploring though, that's ludicrous.

[charlag]

Last time I've checked it was re-downloading the same emails over and over which is not ideal obviously

[murilopereirame]

Seems to be working

First Indexing

{
  "indexingTime": 9,
  "storageTime": 147,
  "preparingTime": 2590,
  "mailcount": 74,
  "storedBytes": 204944,
  "encryptionTime": 80,
  "writeRequests": 640,
  "largestColumn": 231,
  "words": 626,
  "indexedBytes": 46689,
  "downloadingTime": 2501
}

Total Time: 2737

Second Indexing

{
  "indexingTime": 294,
  "storageTime": 446,
  "preparingTime": 12411,
  "mailcount": 308,
  "storedBytes": 2344256,
  "encryptionTime": 366,
  "writeRequests": 1926,
  "largestColumn": 1116,
  "words": 1550,
  "indexedBytes": 4187640,
  "downloadingTime": 11751
}

Total time: 12857