-- pg_tre 3.2.6 -> 4.0.0 upgrade.
--
-- No catalog changes: `diff sql/pg_tre--3.2.6.sql sql/pg_tre--4.0.0.sql`
-- differs only in the header comment's version string.  The SQL surface,
-- the operator classes and the ON-DISK PAGE FORMAT are all unchanged, so
-- **no REINDEX is required**.
--
-- What 4.0.0 changes is the WAL record format.  pg_tre no longer registers
-- a custom resource manager; the write path uses PostgreSQL's generic WAL
-- facility.  Two operational consequences, both documented in CHANGELOG.md
-- under "Breaking changes":
--
--   1. shared_preload_libraries = 'pg_tre' is NO LONGER REQUIRED.  You may
--      remove it after upgrading.  Leaving it set is harmless.
--
--   2. WAL written by pg_tre 3.x cannot be replayed by 4.0.0 and vice
--      versa.  This is NOT a concern for a normal upgrade of a cleanly
--      shut down server, but it does mean:
--        - shut the server down cleanly (a checkpoint on shutdown) before
--          swapping the library, so no 3.x pg_tre WAL remains to replay;
--        - a physical standby cannot run a different pg_tre major than its
--          primary -- upgrade the primary, then rebuild the standby from a
--          fresh base backup.  There is no rolling-upgrade path.
--      Logical replication is unaffected.
--
-- Also note: wal_consistency_checking = 'pg_tre' is now a FATAL startup
-- error, because that resource-manager name no longer exists.  Use
-- wal_consistency_checking = 'all' (generic WAL records are checked under
-- the `generic` resource manager).