Migrating from Fameflower to Goldenrod takes hours

Sobha Duvvuri reported (MODINVSTOR-513) it took 3+ hours for MODINVSTOR to upgrade from 19.1.2 to 19.2.0-snapshot.

For security reasons (RMB-584) the f_unaccent function is moved from "public" database schema to the tenant-module database schema (RMB-583).

Many indexes use an index expression with public.f_unaccent. After the upgrade RMB runs queries using the tenant-module f_unaccent, therefore the upgrade drops all indexes that use public.f_unaccent and recreates them using the tenant-module f_unaccent.

Recreating these indexes take long time. This cannot be avoided for the migration to Goldenrod, but it won't happen again (Goldenrod -> Honeysuckle -> Iris -> ...).

MODINVSTOR-497 is a proposal to create a pre-release that can be installed separately, for example a few days before the actual migration, and creates the new indexes in advance. This doesn't reduce the total time, but the time can be split.

What else can we do to reduce the impact of the long migration?