chore: allow multiple agent subsystems, add exectrace (#8933)

coderd/database/migrations/000148_agent_multiple_subsystems.down.sql

@@ -0,0 +1,17 @@
+BEGIN;
+
+-- Bring back the subsystem column.
+ALTER TABLE workspace_agents ADD COLUMN subsystem workspace_agent_subsystem NOT NULL DEFAULT 'none';
+
+-- Update all existing workspace_agents to have subsystem = subsystems[0] unless
+-- subsystems is empty.
+UPDATE workspace_agents SET subsystem = subsystems[1] WHERE cardinality(subsystems) > 0;
+
+-- Drop the subsystems column from workspace_agents.
+ALTER TABLE workspace_agents DROP COLUMN subsystems;
+
+-- We cannot drop the "exectrace" value from the workspace_agent_subsystem type
+-- because you cannot drop values from an enum type.
+UPDATE workspace_agents SET subsystem = 'none' WHERE subsystem = 'exectrace';
+
+COMMIT;

coderd/database/migrations/000148_agent_multiple_subsystems.up.sql

@@ -0,0 +1,21 @@
+BEGIN;
+
+-- Add "exectrace" to workspace_agent_subsystem type.
+ALTER TYPE workspace_agent_subsystem ADD VALUE 'exectrace';
+
+-- Create column subsystems in workspace_agents table, with default value being
+-- an empty array.
+ALTER TABLE workspace_agents ADD COLUMN subsystems workspace_agent_subsystem[] DEFAULT '{}';
+
+-- Add a constraint that the subsystems cannot contain the deprecated value
+-- 'none'.
+ALTER TABLE workspace_agents ADD CONSTRAINT subsystems_not_none CHECK (NOT ('none' = ANY (subsystems)));
+
+-- Update all existing workspace_agents to have subsystems = [subsystem] unless
+-- the subsystem is 'none'.
+UPDATE workspace_agents SET subsystems = ARRAY[subsystem] WHERE subsystem != 'none';
+
+-- Drop the subsystem column from workspace_agents.
+ALTER TABLE workspace_agents DROP COLUMN subsystem;
+
+COMMIT;