pg-db-usage

#!/usr/bin/env ruby

# Assumes `psql` is able to run without additional arguments on your machine.
# This usually means you need to have a database name that matches your
# username.

Prefixes = %w[k M G]

Prefix = Struct.new :to_s do
  def <=>(other)
    Prefixes.index(to_s) <=> Prefixes.index(other.to_s)
  end
end

Db = Struct.new :name, :size, :unit do
  def initialize(name, size)
    super name, size.to_i, Prefix.new(size[-2])
  end

  def valid?
    size.nonzero?
  end

  def <=>(other)
    unit_comparison = unit <=> other.unit
    if unit_comparison.zero?
      size <=> other.size
    else
      unit_comparison
    end
  end

  def to_s
    "#{name.ljust(30)} #{size.to_s.rjust(5)} #{unit}B"
  end
end

line_to_db = ->(line) {
  name, size = line.split("|").map(&:strip).values_at(0, 6)
  Db.new(name, size)
}

parse_psql_output = ->(_) {
  _
    .each_line
    .drop_while { |l| !l.start_with? "---" }
    .drop(1)
    .take_while { |l| !l.start_with? "(" }
    .map(&line_to_db)
    .select(&:valid?)
    .sort
    .reverse
}

puts IO.popen('psql -c "\l+"', &parse_psql_output)

bridge-dev-dump                   12 GB
bridge_test_api                   58 MB
meolabot                          30 MB
clients-service-test              12 MB
pzs_development                 8572 kB
iracingplanner_dev              7073 kB
madebybears_production          6721 kB
madebybears_development         6721 kB
postgres                        6620 kB
miha                            6620 kB
ectotest                        6593 kB
interview_test                  6513 kB
madebybears_test                6505 kB
template1                       6505 kB
bridge-test                     6505 kB
template0                       6497 kB