实体框架核心：如果我们永远不会还原迁移，删除Migration.Designer.cs是否安全？ [英] Entity Framework Core: Is it safe to delete Migration.Designer.cs if we will never Revert a migration?

问题描述

我们有一个包含约200个表的数据库架构。
为每次迁移创建的模型快照（Migration.Designer.cs）约为2万行。因此，进行大量迁移确实会减慢我们在CI上的构建速度（使用〜30个迁移构建解决方案需要6分钟（如果不进行迁移，则需要4分钟）。

We have a database schema with ~200 tables. Model snapshot (Migration.Designer.cs) which is created for each migration is ~20K lines. So, having quite a number of migrations really slows down our build on CI (with ~30 migrations building a solution takes 6 minutes with migrations or 4 minutes without them).

那么，问题来了：删除旧迁移的模型快照是否安全（我们知道我们永远不会还原）？

So, to the question: is it safe to delete model snapshots for old migrations (that we know we will never Revert)? Are model snapshots used for anything else except Revert-Migration?

推荐答案

模型快照是否用于任何其他用途？

Are model snapshots used for anything else except Revert-Migration?

是的。在一些需要的情况下。在SQL Server上，这些情况是：

Yes. There are a few edge cases where it's needed. On SQL Server, those cases are:

• 当列变窄或计算表达式更改并且索引需要重建时，AlterColumn


• 在索引唯一且引用可为空的列时在内存优化表上创建索引

在大多数情况下，删除它可能是安全的，但是请在执行此操作后测试您的迁移是否仍然有效。

So most of the time it's probably safe to delete, but please test that your migrations still work after doing so.

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