MC-181278Optimizing old Minecraft 1.0 worlds deletes their data
The bug
When optimizing old worlds (e.g. from Minecraft 1.0) their data is deleted.
Expected would be either, that
- optimizing includes upgrading (if necessary)
- optimizing older / unknown versions is not supported
- the warning text on the "Optimize World" screen is clearer and only shown when optimizing an older world, see MC-181274
How to reproduce
- Create a world in Minecraft 1.0 or download test 1.0.zip
- Open the latest version and in the world selection, click "Edit"
- Select "Optimize world"
Note that the world now shows the current version as version on the world selection screen - Open the word
You are spawned in the middle of the ocean (you should be in a swamp)
Linked Issues
Attachments1
Created Issue:
Optimizing old Minecraft 1.0 worlds deletes their data
The bug
When optimizing old worlds (e.g. from Minecraft 1.0) their data is deleted.
Expected would be either, that
- optimizing includes upgrading (if necessary)
- optimizing older / unknown versions is not supported
- the warning text on the "Optimize World" screen is clearer and only shown when optimizing an older world, see MC-181274
How to reproduce
- Create a world in Minecraft 1.0 or download test 1.0.zip
- Open the latest version and in the world selection, click "Edit"
- Select "Optimize world"
- Open the word
Attachments1
is blocked by
![[Mod] NeunEinser](../../../data/avatars/users/39263.png){kind=small}
relates to
![[Mod] Michael Wobst](../../../data/avatars/users/37868.png){kind=small}
![[Mod] Greymagic27](../../../data/avatars/users/92875.png){kind=small}
The bug
On the world selection screen, when clicking "Edit" and then selecting "Optimize World", the following text (translation key optimizeWorld.confirm.description) is shown:
This will attempt to optimize your world by making sure all data is stored in the most recent game format. This can take a very long time, depending on your world. Once done, your world may play faster but will no longer be compatible with older versions of the game. Are you sure you wish to proceed?
The highlighted text is rather misleading. This text appears always, even if the world has been opened in the current version already and can therefore be misunderstood that downgrading is normally supported (which it is not).
Additionally it does not indicate clearly enough that optimizing a world which has not been upgraded yet, potentially corrupts the world / deletes information (see MC-181278, which might be the intended meaning of the sentence).
Please test by creating an old world, placing a user placed block then upgrading, I believe the user placed block will remain, the rest of the terrain is world seed generated, due to the changes in seed format to add biomes the original spawn seed will be different between versions accounting for your swamp to ocean change, as placed blocks are stored seperately to keep the world size down the placed block should remain in situ.
This also happens between using a 32 bit seed on bedrock and the same seed in the 64 bit java version, since the output is different.
A fix could be done by noting the limited biomes for the explored area and optimising for that limited number then allowing exploration the full extent of biomes beyond the explored area.
Or for a really old world convert whole chunks to placed blocks for format optimization, takes more storage but would keep older terrain.
A final option would be to class old explored biomes as classic biomes, overriding the new biomes when optimised.
I'm pretty sure what happens is the game doesn't recognize the McRegion level format and so just doesn't deal with it at all and instead just generates a new world entirely. The game should ideally convert any McRegion worlds to Anvil when a player uses the Optimize World option before it does anything else.
Seems like the game completely ignores the old *.mcr files.
It doesn't delete the old files, and you should still be able to play it when put back into 1.0.
Can confirm in 1.17.1. You are spawned in what seems to be a swamp but is actually a deep ocean biome.
(Also the world gets abruptly cut off at chunk borders, but I assume that is unfixable).
I don't think this is an issue anymore since for example 1.18.2 now no longer allows you to load or optimize the world, but tells you to load it in an older version instead.
Does this still apply to worlds from 12w07a onwards?