Add reindexing doc

docs/src/SUMMARY.md

@@ -15,6 +15,7 @@
     - [Sparrow Wallet](guides/collecting/sparrow-wallet.md)
   - [Testing](guides/testing.md)
   - [Moderation](guides/moderation.md)
+  - [Reindexing](guides/reindexing.md)
 - [Bounties](bounties.md)
   - [Bounty 0: 100,000 sats Claimed!](bounty/0.md)
   - [Bounty 1: 200,000 sats Claimed!](bounty/1.md)

docs/src/guides/reindexing.md

@@ -0,0 +1,32 @@
+Reindexing
+==========
+
+Sometimes the `ord` database must be reindexed, which means deleting the
+database and restarting the indexing process with either `ord index run` or
+`ord server`. Reasons to reindex are:
+
+1. A new major release of ord, which changes the database scheme
+2. The database got corrupted somehow
+
+The database `ord` uses is called [redb](https://github.com/cberner/redb),
+so we give the index the default file name `index.redb`. By default we store this
+file in different locations depending on your operating system.
+
+|Platform | Value                                            | Example                                      |
+| ------- | ------------------------------------------------ | -------------------------------------------- |
+| Linux   | `$XDG_DATA_HOME`/ord or `$HOME`/.local/share/ord | /home/alice/.local/share/ord                 |
+| macOS   | `$HOME`/Library/Application Support/ord          | /Users/Alice/Library/Application Support/ord |
+| Windows | `{FOLDERID_RoamingAppData}`\ord                  | C:\Users\Alice\AppData\Roaming\ord           |
+
+So to delete the database and reindex on MacOS you would have to run the following
+commands in the terminal:
+
+```bash
+rm ~/Library/Application Support/ord/index.redb
+ord index run
+```
+
+You can of course also set the location of the data directory yourself with `ord
+--data-dir <DIR> index run` or give it a specific filename and path with `ord
+--index <FILENAME> index run`.
+