-- pg_turbovec v1.18.0 -- Tier-1 IVF latency optimizations (scan-path).
--
-- This file is a *reference mirror*. The authoritative install
-- script is generated by `cargo pgrx schema`.
--
-- v1.18.0 closes the Tier-1 IVF-latency backlog
--. All changes are SCAN-PATH /
-- default-tuning only -- NO SQL surface change, NO wire-format change
-- (MetaPageData::version stays 5; single-vector indexes stay v4),
-- and NO REINDEX is required.
--
--   #1a: the default turbovec.search_k is lowered 100 -> 32. The
--        per-query latency floor is the executor's reorder-recheck of
--        every returned candidate (a heap fetch + an exact
--        full-precision distance recompute each); the recall-vs-
--        search_k frontier shows recall@10 plateaus by ~25, so the
--        old default of 100 over-provisioned the recheck ~3x for zero
--        recall gain. Existing indexes are unaffected; the new
--        default simply changes how many candidates a scan rechecks.
--        Raise it for queries with LIMIT > ~20 or to push recall on a
--        hard corpus; lower it (toward 16) for the lowest latency.
--
--   #2:  documented + test-verified guidance that raising
--        WITH (assign_dups = M) (soft multi-assignment) lets a query
--        reach a matched recall while probing FEWER cells (lower
--        latency at matched recall). assign_dups > 1 is a build-time
--        layout choice and requires a REINDEX to take effect; it is
--        OPT-IN and the default (1) is unchanged.
--
--   #1b (advertise a tighter orderby distance) was investigated and
--   REJECTED as a no-op (PostgreSQL rechecks every returned candidate
--   unconditionally under xs_recheckorderby). #3-6 were assessed and
--   deferred / not-warranted-by-data. See the plan doc.
--
-- There is no DDL and no on-disk migration. `ALTER EXTENSION
-- pg_turbovec UPDATE TO '1.18.0';` resolves against this
-- intentionally-empty file. The default-GUC change takes effect for
-- new sessions; no index rebuild is needed.