hummingbird-me/kitsu-server

#!/usr/bin/env ruby
# frozen_string_literal: true
require 'securerandom'

# This script takes a CSV file on STDIN and outputs a SQL script that will import the CSV into a new
# table with the same schema as the specified base table, then safely hot-swap the new table in for
# the base table before deleting it. This allows us to import a whole dataset in one go without
# locking the table for reads.

base_table = ARGV[0]
new_table = "#{base_table}_#{SecureRandom.alphanumeric(5)}"
old_table = "#{new_table}_old"

def tee(str)
  $stdout.puts str
  $stderr.puts str
end

tee "BEGIN;"

tee "CREATE TABLE #{new_table} (LIKE #{base_table} INCLUDING ALL);"
tee "COPY public.#{new_table} FROM stdin WITH (FORMAT csv, FREEZE true);"

$stdin.each_line { |line| puts line }

puts "\\."

tee "ALTER TABLE #{base_table} RENAME TO #{old_table};"
tee "ALTER TABLE #{new_table} RENAME TO #{base_table};"
tee "DROP TABLE #{old_table} CASCADE;"

tee "COMMIT;"