Is it possible combine remote results to local a register in Ansible?

I'm trying to gather information on a mysql cluster in order to then use in some local logic.

My trouble is if I run my command on the remote hosts I won't have access to those results

- name: get uuids for existing cluster nodes
  shell: mysql -N -B -u {{ db_user }} -p {{ db_user_password }} -e "SHOW GLOBAL STATUS LIKE 'wsrep_cluster_state_uuid';" | sed 's/\t/,/g' | cut -f2 -d','
  register: maria_cluster_uuids

This gives me the data I need but what I'd really like is a combined list/dict of the results.

I could try:

- name: get uuids for existing cluster nodes
  run_once: true
  shell: mysql -N -B -u {{ db_user }} -h {{ item }} -p {{ db_user_password }} -e "SHOW GLOBAL STATUS LIKE 'wsrep_cluster_state_uuid';" | sed 's/\t/,/g' | cut -f2 -d','
  register: maria_cluster_uuids
  with_items: play_hosts
  delegate_to: 127.0.0.1

however, mysql kicks up a warning and to be honest, I don't want to impose a requirement of the local machine having a mysql client installed.

Nasty feeling I'm going to have to write some python here...

Use set_fact module and hostvars:

---
- hosts: all
  vars:
    uuids: |
      {%- set o=[] %}
      {%- for i in play_hosts %}
        {%- if o.append(hostvars[i].uuid) %}
        {%- endif %}
      {%- endfor %}
      {{ o }}
  tasks:
    - name: get uuids for existing cluster nodes
      shell: mysql -N -B -u {{ db_user }} -p {{ db_user_password }} -e "SHOW GLOBAL STATUS LIKE 'wsrep_cluster_state_uuid';" | sed 's/\t/,/g' | cut -f2 -d','
      register: maria_cluster_uuids
    - set_fact:
        uuid: "{{ maria_cluster_uuids.stdout }}"
    - debug:
        var: uuids
      run_once: true
      delegate_to: 127.0.0.1

Would it help to write the output of the mysql command on the local host or ansible host, and keep on appending the results from all the servers. Once done, you can parse that file within your playbook, or even write a parser script and execute if from the playbook.

Collecting the output would look something like this -

---
- hosts: production
  tasks:
  - name: get uuids for existing cluster nodes
    shell: mysql -N -B -u {{ db_user }} -p {{ db_user_password }} -e "SHOW GLOBAL STATUS LIKE 'wsrep_cluster_state_uuid';" | sed 's/\t/,/g' | cut -f2 -d','
    register: maria_cluster_uuids

  - name: Write to local disk
    lineinfile: dest=/tmp/mysqlcluster create=yes line="{{ maria_cluster_uuids.stdout_lines }}"
    delegate_to: 127.0.0.1

Then you can parse /tmp/mysqlcluster file.