Ugly/slow/unoptimized/naive PoC r/place exporter from DB to PNG

rplace.rb

#!/usr/bin/ruby

require 'io/console'
require 'pg'
require 'chunky_png'

WIDTH = 2000
HEIGHT = 2000
ROWS = 10000
OUTFILE = 'rplace.png'

UNTIL = '2022-04-04 18:00:00'

begin
    puts "RPlaceRender v0.1 (C) Akos Kovacs"
    pass = IO::console.getpass "DB Password: "
    con = PG.connect :dbname => 'rplace', :user => 'akos', :password => pass
    png = ChunkyPNG::Image.new(WIDTH, HEIGHT, ChunkyPNG::Color::TRANSPARENT)

    puts "User: #{con.user} Database name: #{con.db}"
    con.transaction do
      con.exec "DECLARE curhist SCROLL CURSOR FOR SELECT h.id, pos_x, pos_y, pixel_color, timestamp FROM history h JOIN palette p ON h.palette_id = p.id WHERE timestamp <= '#{UNTIL}' ORDER BY timestamp ASC"
      x = y = hexcolor = timestamp = nil
      while true
        rows = con.exec "FETCH FORWARD #{ROWS} FROM curhist"
        #puts "FETCHed #{rows.ntuples}..."
        
        #puts "(#{x}, #{y}) = '#{hexcolor}' @ [#{timestamp}] first of #{rows.ntuples} ROWS" if x != nil
        #rows.fields.collect.each_with_index { |r, i| puts "#{i}. - #{r}" }
        #puts rows.fields.collect {|fname| "%-15s" % [fname] }.join( '' )
        if rows.ntuples == 0
          puts "No other rows remained, quit."
          con.exec "CLOSE curhist"
          break
        end

        rows.each do |row|
          x = row["pos_x"].to_i
          y = row["pos_y"].to_i
          hexcolor = row["pixel_color"]
          timestamp = row["timestamp"]
          #puts "(#{x}, #{y}) = '#{hexcolor}' @ [#{timestamp}]"
          png[x, y] = ChunkyPNG::Color.from_hex(hexcolor)
        end
      end
    end
    png.metadata['Author'] = 'RPlaceRender by Akos Kovacs'
    png.save("#{UNTIL}_#{OUTFILE}", :fast_rgba)
    
rescue PG::Error => e
    puts e.message 
ensure
    con.close if con
end