实现套餐生效条件覆盖与购买快照

migrations/000163_add_package_usage_terms_snapshots.up.sql

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+-- 为套餐使用记录增加购买时不可变计时条款快照；空值和零值保留为历史未快照标记。
+ALTER TABLE tb_package_usage
+    ADD COLUMN expiry_base_snapshot VARCHAR(30) NOT NULL DEFAULT '',
+    ADD COLUMN calendar_type_snapshot VARCHAR(20) NOT NULL DEFAULT '',
+    ADD COLUMN duration_months_snapshot INTEGER NOT NULL DEFAULT 0,
+    ADD COLUMN duration_days_snapshot INTEGER NOT NULL DEFAULT 0;
+
+COMMENT ON COLUMN tb_package_usage.expiry_base_snapshot IS '购买时生效条件快照，空字符串表示历史未快照';
+COMMENT ON COLUMN tb_package_usage.calendar_type_snapshot IS '购买时周期类型快照，空字符串表示历史未快照';
+COMMENT ON COLUMN tb_package_usage.duration_months_snapshot IS '购买时月数快照，0表示未使用或历史未快照';
+COMMENT ON COLUMN tb_package_usage.duration_days_snapshot IS '购买时天数快照，0表示未使用或历史未快照';
+
+-- 触发器只校验新记录及快照字段变更，历史空快照仍可更新状态等非快照字段。
+CREATE OR REPLACE FUNCTION validate_package_usage_terms_snapshot()
+RETURNS TRIGGER AS $$
+BEGIN
+    IF NEW.expiry_base_snapshot NOT IN ('from_purchase', 'from_activation')
+        OR NOT (
+            (NEW.calendar_type_snapshot = 'natural_month' AND NEW.duration_months_snapshot > 0 AND NEW.duration_days_snapshot = 0)
+            OR (NEW.calendar_type_snapshot = 'by_day' AND NEW.duration_days_snapshot > 0 AND NEW.duration_months_snapshot = 0)
+        ) THEN
+        RAISE EXCEPTION '套餐使用记录计时快照不完整或无效';
+    END IF;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER trg_validate_package_usage_terms_snapshot
+BEFORE INSERT OR UPDATE OF expiry_base_snapshot, calendar_type_snapshot, duration_months_snapshot, duration_days_snapshot
+ON tb_package_usage
+FOR EACH ROW
+EXECUTE FUNCTION validate_package_usage_terms_snapshot();