how to search for entries where a custom field is either not present or is empty

Question

Some of my entries have the optional plaintext field myCustomField. I want to retrieve all entries except those where myCustomField is filled out.

I can get all entries that have an empty myCustomField

craft.entries({
    myCustomField: ':empty:',
})

but that doesn't include entries that don't have the field myCustomField.

Answer 1

I don't know if you can do that at query level without adding the field to your other sections but you can do (although it's not very economical):

{% set entries = craft.entries.all() %}

{% for entry in entries %}
{% if entry.text is empty %}
    {{ entry.title }} <br>
{% endif %}
{% endfor %}

Answer 2

I've found that this is possible for lightswitch fields:

craft.entries.myLightswitchField(':empty:')

aka

craft.entries({
    myLightswitchField: ':empty:'
})

returns all entries where the lightswitch field is toggled off and entries that don't have the lightswitch field.

Not a solution for my text field need, but similar enough that it may be useful for other people.