$setUnion
Reference group: Array aggregation expressions
What it does
Returns unique elements across arrays; output order is not guaranteed.
Syntax
{$setUnion: [array1, array2, ...]}
Use case
Deduplicate tags.
$setUnion: practical example
{ $project: { tags: { $setUnion: ["$tags", "$extraTags"] } } }💡 Explanation
Returns unique elements across arrays; output order is not guaranteed.
When to use it
Deduplicate tags.
Key Takeaways
- Returns unique elements across arrays; output order is not guaranteed.
- Typical use: Deduplicate tags.