firebase-database@0.5.22

Support aggregate by pipeline:

example 7
# orderByChild('status').equalTo('A') and get first 3 elements with sorting by name field in a non case-sensitive manner.
ref.aggregate([
  { $match: { status: 'A' }},
  { $project: { name: 1, lower_name: { $toLower: '$name' } } },
  { $sort: { lower_name: 1 } },
  { $limit: 3 }
])