sql: block on transition to multi-region if tables have custom zone configs

[aayushshah15]

Address this TODO:


cockroach/pkg/sql/alter_database.go

Line 759 in fddcc70

// TODO(#57668): check zone configurations are not set here

When attempting to transition an existing database to multi-region, we’d like to block the transition if any existing tables within the database have custom constraints, voter_constraints, num_replicas, num_voters or lease_preferences defined. We expect the user to DISCARD these existing configs before they can add their initial primary region.

Without the above, we risk clobbering the individual tables’ zone configs upon the transition, as they may not inherit attributes that, for instance, control the survivability or attributes that dictate the placement of non-voting replicas.

Lastly, we might want to permit the user to force their way into this transition if they have the override_multi_region_zone_config session variable set to true.

To reproduce:

root@127.0.0.1:26257/db> create table t ();

root@127.0.0.1:26257/db> alter table t configure zone using num_replicas=3, constraints='{"+region=europe-west1": 1}';

root@127.0.0.1:26257/db> alter database db configure zone using num_replicas=5, constraints='{"+region=europe-west1": 5}';

root@127.0.0.1:26257/db> alter database db set primary region "us-east1";

root@127.0.0.1:26257/db> show zone configuration for table t;
  target  |                 raw_config_sql
----------+-------------------------------------------------
  TABLE t | ALTER TABLE t CONFIGURE ZONE USING
          |     range_min_bytes = 134217728,
          |     range_max_bytes = 536870912,
          |     gc.ttlseconds = 90000,
          |     num_replicas = 3,
          |     num_voters = 3,
          |     constraints = '{+region=europe-west1: 1}', <-- ??
          |     voter_constraints = '[+region=us-east1]',
          |     lease_preferences = '[[+region=us-east1]]'

[blathers-crl]

Hi @aayushshah15, please add branch-* labels to identify which branch(es) this release-blocker affects.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is otan.}

[otan]

Lastly, we might want to permit the user to force their way into this transition if they have the override_multi_region_zone_config session variable set to true.

filing this as a separate issue