Counting in AQL
You can count the documents of a collection in different ways
To return the count of documents that currently exist in a collection, you can call the LENGTH() function:
This type of call is optimized since 2.8 (no unnecessary intermediate result is built up in memory) and it is therefore the preferred way to determine the count. Internally, COLLECTION_COUNT() is called.
In earlier versions with
COLLECT ... WITH COUNT INTO available (since 2.4),
you may use the following code instead of LENGTH() for better performance:
FOR doc IN collection COLLECT WITH COUNT INTO length RETURN length