Not able to modify the zone configuration for the system.jobs table directly

[rkruze]

Describe the problem

Please describe the issue you observed, and any steps we can take to reproduce it:

When I go running the following command

ALTER TABLE system.public.jobs CONFIGURE ZONE USING                                                                                                                                                                                                                                                                                                     range_min_bytes = 16777216,                                                                                                                                                                                                                                                                                                                                                      range_max_bytes = 134217728,                                                                                                                                                                                                                                                                                                                                                     gc.ttlseconds = 600,                                                                                                                                                                                                                                                                                                                                                             num_replicas = 5,                                                                                                                                                                                                                                                                                                                                                                constraints = '[]',                                                                                                                                                                                                                                                                                                                                                              lease_preferences = '[]';

I would expect that when I go to the range report for the ranges making up the jobs table that they would state 128 MiB for Max Range Size Before Split. However, after the alter table command above it still shows 64 MiB. It is only when I do the following that I see the value for this range change:

ALTER DATABASE system CONFIGURE ZONE USING
	range_min_bytes = 16777216,
	range_max_bytes = 134217728,
	gc.ttlseconds = 90000,
	num_replicas = 5,
	constraints = '[]',
	lease_preferences = '[]'

Environment:

• CockroachDB version 19.1.3
• Server OS: Linux

[bdarnell]

Indeed:

cockroach/pkg/config/system.go

Lines 259 to 263 in d05f199

	// For now, you can only set a zone config on the system database as a whole,
	// not on any of its constituent tables. This is largely because all the
	// "system config" tables are colocated in the same range by default and
	// thus couldn't be managed separately.
	objectID = keys.SystemDatabaseID

The simple fix is to change MaxReservedDescID to MaxSystemConfigDescID. This will create the slightly odd situation in which it's possible to set zone configs on some tables but not others (the gossiped tables will still ignore their zone configs in favor of the database-level one), but it would at least let us set zone configs on the jobs table.

[bdarnell]

Note that this applies to both manual zone config changes like the one described here and the default zone config that sets the GC for this table (since version 2.0). So the jobs table has in practice been getting the default 24h gc instead of the intended 10m.