added triggers for user balance calculation

sql/shard.sql

@@ -40,3 +40,53 @@ INSERT INTO ledger_statuses (status_id, name) VALUES
 (2, 'ratified'),
 (3, 'disputed'),
 (4, 'settled');
+
+DELIMITER //
+CREATE TRIGGER after_ledger_insert
+AFTER INSERT ON ledger
+FOR EACH ROW
+BEGIN
+    IF NEW.status_id = 1 THEN
+        UPDATE user_balances
+        SET total_pending = total_pending + NEW.amount
+        WHERE user_id = NEW.user_id AND currency_code = NEW.currency_code;
+    ELSEIF NEW.status_id IN (2, 4) THEN
+        UPDATE user_balances
+        SET total_confirmed = total_confirmed + NEW.amount
+        WHERE user_id = NEW.user_id AND currency_code = NEW.currency_code;
+    END IF;
+END //
+CREATE TRIGGER after_ledger_update
+AFTER UPDATE ON ledger
+FOR EACH ROW
+BEGIN
+    IF OLD.status_id = 1 THEN
+        UPDATE user_balances SET total_pending = total_pending - OLD.amount
+        WHERE user_id = OLD.user_id AND currency_code = OLD.currency_code;
+    ELSEIF OLD.status_id IN (2, 4) THEN
+        UPDATE user_balances SET total_confirmed = total_confirmed - OLD.amount
+        WHERE user_id = OLD.user_id AND currency_code = OLD.currency_code;
+    END IF;
+    IF NEW.status_id = 1 THEN
+        UPDATE user_balances SET total_pending = total_pending + NEW.amount
+        WHERE user_id = NEW.user_id AND currency_code = NEW.currency_code;
+    ELSEIF NEW.status_id IN (2, 4) THEN
+        UPDATE user_balances SET total_confirmed = total_confirmed + NEW.amount
+        WHERE user_id = NEW.user_id AND currency_code = NEW.currency_code;
+    END IF;
+END //
+CREATE TRIGGER after_ledger_delete
+AFTER DELETE ON ledger
+FOR EACH ROW
+BEGIN
+    IF OLD.status_id = 1 THEN
+        UPDATE user_balances SET total_pending = total_pending - OLD.amount
+        WHERE user_id = OLD.user_id AND currency_code = OLD.currency_code;
+    ELSEIF OLD.status_id IN (2, 4) THEN
+        UPDATE user_balances SET total_confirmed = total_confirmed - OLD.amount
+        WHERE user_id = OLD.user_id AND currency_code = OLD.currency_code;
+    END IF;
+END //
+DELIMITER ;
+
+