hcsv - dump id + values from one hstore column

hcsv

#!/usr/bin/env ruby
# Usage: hcsv DBNAME TBLNAME HSTORECOL 
# Output columns will be id + all the hstore keys

dbname, tblname, hstorecol = ARGV[0..2]

# Get hstore keys
out = `psql #{dbname} --tuples --command "SELECT DISTINCT k FROM (SELECT skeys(#{hstorecol}) AS k FROM #{tblname}) AS dt ORDER BY k"`
headers = out.split(/\n/).map(&:strip)

# Dump CSV of id + all hstore keys
hstore_headers_sql = headers.map { |k| %{#{hstorecol}->'#{k}' AS "#{k}"} }.join(', ')
system 'psql', dbname, '--tuples', '--command', "COPY (SELECT id, #{hstore_headers_sql} FROM #{tblname}) TO STDOUT (FORMAT 'csv', HEADER)"