save data Clearing world generation data from a save file so it can be changed. And how to fix World Generation corruption in a save file.

[Jack_Frost]

I am running a large server and ran into a problem of the server's save file being corrupted, so I figured I would document my diagnosis and fix. 
Symptoms

• New generated chunks being nothing but void
• /wgen regen generating empty chunks
• Able to place blocks in empty chunks
• Can move freely inside empty chunks
• No error logs in world gen or server main log

Diagnosis steps:

1. First step I did was check to see if it was chunk corruption or a failure to generate new chunks. I did so by seeing if blocks could be placed inside the chunks that were showing signs of errors
2. I tested /wgen regen in several already generated older chunks to see if the problem was isolated to the world generation or just the regen command
3. I started a fresh save file with the same exact mods, configs, and seed to see if the issue was the server backend or a save file issue
4. After narrowing the issue down to the save file I read this wiki doc to see how the save file is contructed. https://wiki.vintagestory.at/Modding:VCDBS_format
5. After seeing the different tables and what purpose they serve, I concluded that the MapRegion table was corrupted.

The Fix

1. Generate back up of server save using:

   Quote

   /genbackup

2. Stop the server
3. Rename Default.vcdbs to: oldsave.vcdbs
4. Generate a new save file with the same mods, configs, and serverconfig. This can be done by starting the server again after changing the name of the save; afterwards stop the server.
   *It is important that if you are changing minor terrain gen that you change it before this step.
5. Rename the new Default.vcdbs to newsave.vcdbs
6. Download SQLite3 via terminal command: (I am on a Ubuntu server)

   Quote

   apt install sqlite3

7. Drag the old save file and the new save file into the same folder 
8. Run this SQL command:

   sqlite3 oldsave.vcdbs <<'SQL'
   ATTACH DATABASE 'newsave.vcdbs' AS newdb;
   
   DELETE FROM mapregion;
   
   INSERT INTO mapregion (position, data)
   SELECT position, data
   FROM newdb.mapregion;
   
   DETACH DATABASE newdb;
   SQL

9. You can check if it worked by running:

   sqlite3 oldsave.vcdbs "SELECT COUNT(*) FROM mapregion;"

   It should have a really small number. mine was 16

10. Delete the new save file as it is no longer needed. It is named "newsave.vcdbs"
11. Rename the old save file back to: "Default.vcdbs"
12. Start the server
13. Run over to the old empty chunks and stand inside them.
14. Regenerate these chunks using the /wgen regen command

The empty chunks should regenerate as they did before.

Edited August 15 by Jack_Frost
forgot a detail and updated info

[Professor Dragon]

Great documentation. You could always add it to the Guides thread: https://www.vintagestory.at/forums/forum/32-guides/

P.D.

[Jack_Frost]

5 hours ago, Professor Dragon said:

Great documentation. You could always add it to the Guides thread: https://www.vintagestory.at/forums/forum/32-guides/

P.D.

I thought I did but I can make another post if that's allowed? I don't want to spam

[Professor Dragon]

7 hours ago, Jack_Frost said:

I thought I did but I can make another post if that's allowed? I don't want to spam

I say that it's fine.

We don't really have strict admins. who police that type of thing.
(But then again, I'm just some person on a forum.)

P.D.

Edited August 15 by Professor Dragon