#1698 moved the library boundary into FileCommentPolicy, where it
belongs, and said plainly what that cost: the moderation screen went
from 65 queries to 465 for a client-scoped moderator with five assigned
clients. Measured here, those numbers are exactly right.
The cost is not in asking. It is that StaffLibraryScope::files() rebuilds
its query every time, and building one runs four immediate lookups per
assigned client — the client's group ids, the same ids again inside
Folder::sharedFolderIds(), that method's own assignment lookup, and the
shared-folder get() in Folder::scopeVisibleToClient(). None of them
depend on the query being built. Gate resolves a fresh policy for every
check, so a listing paid for all of it once per row.
The built query is now memoised per user and handed back as a clone,
since every caller adds to it, and the scope is registered as `scoped`
rather than transient so the memo survives a request. Scoped rather than
a singleton on purpose: a long-lived queue worker keeps singletons
between jobs, and a library query built from one job's data has no
business answering the next one's question.
That is 465 queries down to 60 on the same page — below the 65 it cost
before #1698, because the memo also helps the callers that were already
asking repeatedly. FileVersions::sharedAudience(), which runs the same
helper twice per candidate while resolving notification recipients, gets
it for free.
So the answer to the question #1698 left open is neither of the two it
offered. can_delete stays a real question asked of the policy; nothing
restates the boundary; and the page is faster than it was before the
fix. Three tests: one user's query never answers another's, one caller's
constraints never follow the next, and the moderation screen does not
ask once per row.
ignacionelson