Added upgrade notes [skip ci]

CHANGELOG.md

@@ -1,7 +1,9 @@
 ## 0.3.1 (unreleased)
 
+If upgrading from 0.2.7 or 0.3.0, [recreate](https://github.com/pgvector/pgvector#0-3-1) all `ivfflat` indexes after upgrading to ensure all data is indexed.
+
+- Fixed issue with inserts silently corrupting `ivfflat` indexes (introduced in 0.2.7)
 - Fixed segmentation fault with index creation when lists > 6500
-- Fixed issue with uninitialized pages
 
 ## 0.3.0 (2022-10-15)
 

README.md

@@ -270,6 +270,22 @@ Install the latest version and run:
 ALTER EXTENSION vector UPDATE;
 ```
 
+## Upgrade Notes
+
+### 0.3.1
+
+If upgrading from 0.2.7 or 0.3.0, recreate all `ivfflat` indexes after upgrading to ensure all data is indexed.
+
+```sql
+-- Postgres 12+
+REINDEX INDEX CONCURRENTLY index_name;
+
+-- Postgres < 12
+CREATE INDEX CONCURRENTLY temp_name ON table USING ivfflat (column opclass);
+DROP INDEX CONCURRENTLY index_name;
+ALTER INDEX temp_name RENAME TO index_name;
+```
+
 ## Thanks
 
 Thanks to: