SQLite Forum

single writer, multiple dirty readers
Shared cache mode generally offers less concurrency than wal mode. For starters, all queries will be serialized by a single mutex belonging to the shared cache.

I might be missing something, but I don't think looking to enhance performance by allowing dirty reads really makes much sense in SQLite's single-writer/multi-reader architecture. Each reader sees a version of the database image representing the open snapshot, not a set of rows that need to be filtered to match the open snapshot based on transaction ids and whatnot.