Defer CachedValue updates from post_save/post_delete signal handlers to a
SearchCacheJob that runs after the surrounding transaction commits. Coalesce
pending updates per database alias and savepoint scope, preserving rollback
semantics while reducing synchronous write latency.
When no worker is available, or Redis cannot be reached during dispatch, apply
the update inline so existing single-process installs continue to behave
correctly. Replay the originating database alias during deferred reads and
writes so cache updates remain routed to the schema that emitted the signal.
Keep deferral private to CachedValueSearchBackend so custom SEARCH_BACKEND
implementations continue to use the existing synchronous cache/remove contract.
Move the job runner to search/jobs.py and keep the CachedValue-specific update
logic on the backend.
Document the eventual consistency of global search results and add coverage for
coalescing, rollback/savepoint behavior, worker dispatch, inline fallback,
deleted objects, and the custom backend contract.
Jason Novinger
Daniel Sheppard
jeremystretch