$size
Reference group: Array aggregation expressions
What it does
Returns array length; errors if the resolved value is not an array.
Syntax
{$size: arrayExpr}
Use case
Calculate array length.
Important notes
Use $ifNull and validation for missing/null values.
$size: practical example
{ $project: { tagCount: { $size: { $ifNull: ["$tags", []] } } } }💡 Explanation
Returns array length; errors if the resolved value is not an array.
When to use it
Calculate array length.
Caution
Use
$ifNull and validation for missing/null values.Key Takeaways
- Returns array length; errors if the resolved value is not an array.
- Typical use: Calculate array length.