Compare map.sqlite databases and output a list of changed nodes

compare.lua

-- Usage: lua compare.lua
-- License: MIT License

package.path = "/home/minetest/maplib/?.lua;" .. package.path
local maplib = require( "maplib" )
local config = dofile( "config.lua" )

---------------------------------------

local function printf( ... )
      print( string.format( ... ) )
end

local function compare_blocks( index, new_block, old_block )
	local diff_lines = { }
	local old_node_list = old_block.get_node_list( )
	local old_nodename_map = old_block.nodename_map
	local new_node_list = new_block.get_node_list( )
	local new_nodename_map = new_block.nodename_map

	for idx, new_node in ipairs( new_node_list ) do
		local old_node = old_node_list[ idx ]
		local old_node_name = old_nodename_map[ old_node.id ]
		local new_node_name = new_nodename_map[ new_node.id ]

		if new_node_name ~= old_node_name then
			local pos = maplib.decode_node_pos( idx, index )

			table.insert( diff_lines, string.format( "\t{ pos = { x = %d, y = %d, z = %d }, before = \"%s\", after = \"%s\" },",
				pos.x, pos.y, pos.z, old_node_name, new_node_name ) )
		end
	end

	if #diff_lines > 0 then
		local logfile = assert( io.open( "output/" .. index .. ".txt", "w" ) )
		logfile:write( "return {\n" )
		
		for i, v in ipairs( diff_lines ) do
			logfile:write( v, "\n" )
		end

		logfile:write( "}\n" )
		logfile:close( )
	end

	return #diff_lines
end

-----------------------------------------

local oldmap_db = MapDatabase( config.oldmap_path, false )
local newmap_db = MapDatabase( config.newmap_path, false )

if config.search_area then
	print( "Creating cache..." )
	newmap_db.create_cache( false )
end

print( "Comparing databases..." )

local iterator = config.search_area and
	newmap_db.iterate_area( config.search_area ) or
	newmap_db.iterate( )

for index, new_block in iterator do
	local old_block = oldmap_db.get_mapblock( index )

	if not old_block then
		printf( "[WARNING] Missing block %d in old database!", index )
	else
		local diff_count = compare_blocks( index, new_block, old_block )
		if diff_count > 0 then
			printf( "[INFO] Block %d differs (%d nodes changed).", index, diff_count )
		else
			printf( "[INFO] Block %d matches.", index )
		end
	end
end

print( "Done." )

config.lua

return {
	oldmap_path = "oldmap.sqlite",
	newmap_path = "newmap.sqlite",
	search_area = MapArea( { x = -2, y = -2, z = -2 }, { x = 2, y = 2, z = 2 } ),
}

init.lua

local list = minetest.get_dir_list( "output", false )

minetest.after( 0, function ( )
	for i, v in ipairs( list ) do
		local diff = dofile( "output/" .. v )

		-- use the first node position to forceload the mapblock
		minetest.forceload_block( diff[ 1 ].pos, true )

		for ii, vv in ipairs( diff ) do
			if vv.after == "air" then
				minetest.set_node( vv.pos, { name = "wool:red" } )
			elseif vv.before == "air" then
				minetest.set_node( vv.pos, { name = "wool:green" } )
			else
				minetest.set_node( vv.pos, { name = "wool:yellow" } )
			end
			local meta = minetest.get_meta( vv.pos )
			meta:set_string( "infotext",
				minetest.pos_to_string( vv.pos ) .. "\n" .. vv.before .. " -> " .. vv.after )
		end

		minetest.forceload_free_block( diff[ 1 ].pos, true )
	end
end )