fix: index GetWorkspaceAgentsByResourceIDs query (#5021)

coderd/database/dump.sql

@@ -632,6 +632,8 @@ CREATE UNIQUE INDEX users_email_lower_idx ON users USING btree (lower(email)) WH
 
 CREATE UNIQUE INDEX users_username_lower_idx ON users USING btree (lower(username)) WHERE (deleted = false);
 
+CREATE INDEX workspace_agents_resource_id_idx ON workspace_agents USING btree (resource_id);
+
 CREATE INDEX workspace_resources_job_id_idx ON workspace_resources USING btree (job_id);
 
 CREATE UNIQUE INDEX workspaces_owner_id_lower_idx ON workspaces USING btree (owner_id, lower((name)::text)) WHERE (deleted = false);

coderd/database/migrations/000078_workspace_agents_resource_id_idx.down.sql

@@ -0,0 +1 @@
+DROP INDEX workspace_agents_resource_id_idx;

coderd/database/migrations/000078_workspace_agents_resource_id_idx.up.sql

@@ -0,0 +1 @@
+CREATE INDEX workspace_agents_resource_id_idx ON workspace_agents USING btree (resource_id);