optimize balances view (#1779)

* optimize balances view

flake8

flake8

* fix line length

lnbits/core/migrations.py

@@ -302,3 +302,20 @@ async def m010_create_installed_extensions_table(db):
         );
     """
     )
+
+
+async def m011_optimize_balances_view(db):
+    """
+    Make the calculation of the balance a single aggregation
+    over the payments table instead of 2.
+    """
+    await db.execute("DROP VIEW balances")
+    await db.execute(
+        """
+        CREATE VIEW balances AS
+        SELECT wallet, SUM(amount - abs(fee)) AS balance
+        FROM apipayments
+        WHERE (pending = false AND amount > 0) OR amount < 0
+        GROUP BY wallet
+    """
+    )