Can random be used for ordering with related/assets, in cached code?

Question

I'm trying to determine if I can update this:

{% cache %}
[
{% set tags = craft.tags.group('color','season','style','venue').limit(null) %}
{% for image in craft.assets.relatedTo(tags).order('elements.dateCreated desc') %}
{% set thumbParams = {
    width: 300,
    height:300,
    mode: 'crop'
} %}
{% set smallParams = {
    width: 768,
    mode: 'fit'
} %}
    {
        "url": "{{ image.url }}",
        "filename": "{{ image.filename }}",
        "imageTitle": "{{ image.imageTitle }}",
        "imageThumb": "{{ image.getUrl(thumbParams) }}",
        "tagsColor": [
{% for tag in image.tagsColor %}
        {
            "slug": "{{ tag | slugify }}",
            "tag":  "{{ tag }}"
        }{% if not (loop.last) %},{% endif %}

{% endfor %}
        ],

        "tagsSeason": [
{% for tag in image.tagsSeason %}
            {
            "slug": "{{ tag | slugify }}",
            "tag":  "{{ tag }}"
            }{% if not (loop.last) %},{% endif %}

{% endfor %}
        ],

        "tagsStyle": [
{% for tag in image.tagsStyle %}
            {
            "slug": "{{ tag | slugify }}",
            "tag":  "{{ tag }}"
            }{% if not (loop.last) %},{% endif %}

{% endfor %}
        ],

        "tagsVenue": [
{% for tag in image.tagsVenue %}
            {
            "slug": "{{ tag | slugify }}",
            "tag":  "{{ tag }}"
            }{% if not (loop.last) %},{% endif %}

{% endfor %}
        ]

    }{% if not loop.last %},
{% endif %}

{% endfor %}
]
{% endcache %}

To randomize the order of images. Is that possible with .order and is that possible within cached template code? (As random would be "new" every instance.)

Note that I have the image crops and tag lookups inside the cached code, as those are intensive. The first answer, to shuffle the images after fetching them within the cached code, won't work, because the for loop on the image set is what needs to be cached.

Answer 1

What about composing a custom Twig array containing all the data you need. This does all your DB queries and because you write it in default sort order (randomize afterwards), you can cache all the heavy lifting of your template:

{# Cache an array of fake "ElementModels" #}
{% cache %}

{% set imagesArray = [] %}
{% set tagsColor = [] %}

{% for image in craft.assets %}

    {% for tag in image.tagsColor %}

        {% set tagColor = {
            slug: tag|slugify,
            tag: tag,
        } %}

        {% set tagsColor = tagsColor|merge(tagColor) %}

    {% endfor %}

    {% set imageObject = {
        url: image.url,
        title: image.title,
        tagsColor: tagsColor,
    } %}

    {% set imagesArray = imagesArray|merge(imageObject) %}

{% endfor %}

{% endcache %}

Then randomize your images and print the JSON:

{# Randomize our array #}
{% set imagesArray = shuffle(imagesArray) %}

{# Print the thing into our JSON #}
{% for image in imagesArray %}
    ...
{% endfor %}