* perf: batch-load folders, accounts, and contacts in FetchMailsAsync
Replace the sequential per-mail property-loading loop with a three-step
batch pre-load strategy, eliminating the N+1 DB call pattern that was
the main bottleneck when building the mail list with threading enabled.
Changes:
- Pre-seed the folder cache from MailListInitializationOptions.Folders
so that the most common folders (inbox, sent, etc.) never trigger a DB
lookup at all.
- Load all accounts in a single GetAccountsAsync() call instead of one
GetAccountAsync() call per mail (typically 1–5 accounts total).
- Fetch all sender contacts in a single SQL IN(...) query via the new
GetContactsByAddressesAsync() method instead of one query per address.
- Property assignment is now fully synchronous (no awaits in the loop)
since all data is pre-loaded into plain Dictionary<K,V>.
- Thread-expansion follows the same pattern: new folder IDs are loaded
in parallel via Task.WhenAll; new contact addresses are batch-fetched
with a second IN(...) query.
- Also apply batch pre-loading to GetMailItemsAsync (used by merge-inbox
sync path) which had the same sequential issue.
- Remove the now-unused LoadAssignedPropertiesWithCacheAsync helper and
the ConcurrentDictionary dependency it required.
- Tighten GetMailsByThreadIdsAsync to skip the Id NOT IN clause entirely
when the exclusion set is empty.
https://claude.ai/code/session_018bqahGc6zi95JJhc2aARKS
* test: add MailFetchingTests with correctness and performance coverage
Adds integration tests for MailService.FetchMailsAsync that exercise the
full real-service stack (MailService → FolderService / AccountService /
ContactService) backed by the shared in-memory SQLite helper.
Four tests are included:
• ExpandsSiblingsOutsidePage – proves thread expansion fetches mails that
fall beyond the initial SQL page (6 mails, page=4, expects 6 returned).
• NeverExpandsSiblings – proves threading is truly opt-in; with
CreateThreads=false the result exactly matches the raw page size.
• ResolvesFromAllThreeSources – verifies contact resolution for a known
contact (from the AccountContact table), an unknown sender (ad-hoc
fallback), and a self-sent mail (built from account metadata).
• 1000Mails_70Threads_CompletesWithinBudget – the performance scenario:
1 000 mails (70 threads × 7 + 510 standalone), 40 rotating sender
addresses (20 with DB contacts). Times and reports two scenarios:
- Default first-page fetch (100 mails) + expansion of one partial
thread (expects > 100 mails returned).
- Full load of all 1 000 mails with threading enabled (expects
exactly 1 000 mails returned, all 70 threads intact, < 5 s).
Elapsed times for both scenarios are written to xUnit test output so
they appear in CI logs and can be tracked across builds.
https://claude.ai/code/session_018bqahGc6zi95JJhc2aARKS
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Co-authored-by: Claude <noreply@anthropic.com>
Burak Kaan Köse