A known issue added to README

README.md

@@ -182,6 +182,18 @@ Gossip by default does not include the CJK font because it is larger than all ot
 
 There are so many of these (172) that it becomes a real pain to add them all. But if you need one, please ask (open an issue) and I'll add it for you.
 
+### Known Issues
+
+#### Sqlite Constraint Issues (Foreign or Unique Key)
+
+First you need to locate your database file. The gossip directory is under this path: https://docs.rs/dirs/4.0.0/dirs/fn.data_dir.html  The database file is `gossip.sqlite`.  Then you need to install `sqlite3` on your system.
+
+Using `sqlite3` on your database file, the following kind of SQL can help you identify rows that violate foreign key constraints.
+
+##### Error: Sql(SqliteFailure(Error { code: ConstraintViolation, extended_code: 2067 }, Some("UNIQUE constraint failed: person_relay.person, person_relay.relay")))
+
+You can find which rows are duplicated using: `select a.person, a.relay FROM person_relay a INNER JOIN person_relay b WHERE a.person=b.person AND a.relay=b.relay AND a.rowid!=b.rowid;`  You'll need to delete one row from each pair (by rowid so you don't delete both of them).
+
 ## Technology Involved
 
 - Rust Language