Instead of content:*
try with content:[* TO *]
. That will fetch all documents that have the field content
non-empty.
For querying arrays/multi-valued fields, it depends on what you want to do. If you have a multi-valued field like:
<arr name="tag_names">
<str>death</str>
<str>history</str>
<str>people</str>
<str>historical figures</str>
<str>assassinations</str>
</arr>
and you want to find documents having both death
and history
as tag_names
then issue a query like
q=tag_names:(death AND history)
To do an OR, use
q=tag_names:(death OR history)