Ecto.Query.API.all

You're seeing just the function all, go back to Ecto.Query.API module for more information.

Evaluates whether all values returned from the provided subquery match in a comparison operation.

from p in Post, where: p.visits >= all(
  from(p in Post, select: avg(p.visits), group_by: [p.category_id])
)

For a post to match in the above example it must be visited at least as much as the average post in all categories.

from p in Post, where: p.visits = all(
  from(p in Post, select: max(p.visits))
)

The above example matches all the posts which are tied for being the most visited.

Both any and all must be given a subquery as an argument, and theyu must be used on the right hand side of a comparison. Both can be used with every comparison operator: ==, !=, >, >=, <, <=.