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| author | Yasuo Honda <yasuo.honda@gmail.com> | 2017-08-22 18:49:50 +0000 |
|---|---|---|
| committer | Yasuo Honda <yasuo.honda@gmail.com> | 2017-08-22 19:32:45 +0000 |
| commit | 43c6a683f2caad47b87c5d6a263865cd0db6174f (patch) | |
| tree | 4b737992738b3cd0f59f4aaf22459db3b753be0b /guides/source/active_record_migrations.md | |
| parent | 665ac7cff212d010a3573f85cea895666fbaad15 (diff) | |
| download | rails-43c6a683f2caad47b87c5d6a263865cd0db6174f.tar.gz rails-43c6a683f2caad47b87c5d6a263865cd0db6174f.tar.bz2 rails-43c6a683f2caad47b87c5d6a263865cd0db6174f.zip | |
Load both `:authors` and `:author_addresses` to keep data integrity
`:authors` has a foreign key to `:author_addresses`.
If only `:authors` fixture loaded into the database which supports
foreign key and checks the existing data when enabling foreien keys
like Oracle, it raises the following error
`ORA-02298: cannot validate (ARUNIT.FK_RAILS_94423A17A3) - parent keys not found`
It is because there is no parent data exists in `author_addresses` table.
Here are how other database with foreign key support works:
- MySQL does not check the existing data when enabling foreign key by `foreign_key_checks=1`
https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_foreign_key_checks
> Setting foreign_key_checks to 1 does not trigger a scan of the existing table data. Therefore, rows added to the table while foreign_key_checks=0 will not be verified for consistency.
- PostgreSQL database itself has a feature to check existing data when
enabling foreign key and discussed at #27636, which is reverted.
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