wallet: delete peers with no channels.

ON DELETE CASCADE goes the other way: we should clean up peers with no
channels from db.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/peer_control.c

@@ -181,7 +181,7 @@ static void free_peer(struct peer *peer, const char *why)
 		command_fail(peer->opening_cmd, "%s", why);
 		peer->opening_cmd = NULL;
 	}
-	wallet_channel_delete(peer->ld->wallet, peer->channel->id);
+	wallet_channel_delete(peer->ld->wallet, peer->channel->id, peer->dbid);
 	tal_free(peer);
 }
 

wallet/wallet.c

@@ -866,12 +866,22 @@ void wallet_channel_save(struct wallet *w, struct wallet_channel *chan)
 	tal_free(tmpctx);
 }
 
-void wallet_channel_delete(struct wallet *w, u64 wallet_id)
+void wallet_channel_delete(struct wallet *w, u64 wallet_id, u64 peer_dbid)
 {
 	sqlite3_stmt *stmt;
-	stmt = db_prepare(w->db, "DELETE FROM channels WHERE id=?");
+	/* FIXME: The line to clean up if we're last channel for peer would
+	 * be better as a trigger. */
+	stmt = db_prepare(w->db,
+			  "DELETE FROM channels WHERE id=?");
 	sqlite3_bind_int64(stmt, 1, wallet_id);
 	db_exec_prepared(w->db, stmt);
+
+	stmt = db_prepare(w->db,
+			  "DELETE FROM peers WHERE id = ? AND NOT EXISTS"
+			  " (SELECT 1 FROM channels WHERE peer_id = ?)");
+	sqlite3_bind_int64(stmt, 1, peer_dbid);
+	sqlite3_bind_int64(stmt, 2, peer_dbid);
+	db_exec_prepared(w->db, stmt);
 }
 
 int wallet_extract_owned_outputs(struct wallet *w, const struct bitcoin_tx *tx,

wallet/wallet.h

@@ -225,8 +225,10 @@ void wallet_channel_save(struct wallet *w, struct wallet_channel *chan);
 
 /**
  * wallet_channel_delete -- After resolving a channel, forget about it
+ *
+ * Deletes peer too if no more channels.
  */
-void wallet_channel_delete(struct wallet *w, u64 wallet_id);
+void wallet_channel_delete(struct wallet *w, u64 wallet_id, u64 peer_dbid);
 
 /**
  * wallet_channel_config_save -- Upsert a channel_config into the database