mysql - 使用south迁移数据库表

Question

我没有使用南方。现在我想添加几列。我是不是完蛋了？

(env)noah:code broinjc$ ./manage.py schemamigration reports --initial
Creating migrations directory at '/Users/broinjc/esp/code/reports/migrations'...
Creating __init__.py in '/Users/broinjc/esp/code/reports/migrations'...
 + Added model reports.Classroom
 + Added model reports.Student
 + Added model reports.SurveySet
 + Added model reports.Survey
Created 0001_initial.py. You can now apply this migration with: ./manage.py migrate reports
(env)noah:code broinjc$ ./manage.py migrate reports
Running migrations for reports:
 - Migrating forwards to 0001_initial.
 > reports:0001_initial
FATAL ERROR - The following SQL query failed: CREATE TABLE "reports_classroom" ("id" integer NOT NULL PRIMARY KEY, "user_id" integer NOT NULL, "added" datetime NOT NULL, "updated" datetime NOT NULL, "name" varchar(30) NOT NULL, "am_or_pm" varchar(2) NOT NULL)
The error was: table "reports_classroom" already exists
 ! Error found during real run of migration! Aborting.

 ! Since you have a database that does not support running
 ! schema-altering statements in transactions, we have had 
 ! to leave it in an interim state between migrations.

! You *might* be able to recover with:   = DROP TABLE "reports_classroom"; []
   = DROP TABLE "reports_student"; []
   = DROP TABLE "reports_surveyset"; []
   = DROP TABLE "reports_survey"; []

 ! The South developers regret this has happened, and would
 ! like to gently persuade you to consider a slightly
 ! easier-to-deal-with DBMS (one that supports DDL transactions)
 ! NOTE: The error which caused the migration to fail is further up.
Error in migration: reports:0001_initial

看到这一切后，我想，也许我需要更新我的模型(使它们与 sqlite db 不一致)，所以我更新了它们，然后运行相同的命令，但使用 --auto 而不是初始...

(env)noah:code broinjc$ ./manage.py schemamigration reports --auto
 ? The field 'SurveySet.top_num' does not have a default specified, yet is NOT NULL.
 ? Since you are adding this field, you MUST specify a default
 ? value to use for existing rows. Would you like to:
 ?  1. Quit now, and add a default to the field in models.py
 ?  2. Specify a one-off value to use for existing columns now

...所以我继续选择选项 2，然后继续迁移...

(env)noah:code broinjc$ ./manage.py migrate reports
Running migrations for reports:
 - Migrating forwards to 0002_auto__add_field_surveyset_top_num__add_field_surveyset_externalizer_ra.
 > reports:0001_initial

FATAL ERROR - The following SQL query failed: CREATE TABLE "reports_classroom" ("id" integer NOT NULL PRIMARY KEY, "user_id" integer NOT NULL, "added" datetime NOT NULL, "updated" datetime NOT NULL, "name" varchar(30) NOT NULL, "am_or_pm" varchar(2) NOT NULL)
The error was: table "reports_classroom" already exists
 ! Error found during real run of migration! Aborting.


 ! Since you have a database that does not support running
 ! schema-altering statements in transactions, we have had 
 ! to leave it in an interim state between migrations.

! You *might* be able to recover with:   = DROP TABLE "reports_classroom"; []
   = DROP TABLE "reports_student"; []
   = DROP TABLE "reports_surveyset"; []
   = DROP TABLE "reports_survey"; []

Answer 1

我会尝试解释发生了什么，以便您更好地了解如何做您自己想做的事情。

在使用 South 之前，您的数据库中有一些表，这些表是您首次运行 syncdb 时从模型生成的。

如果您更改模型，例如添加一个字段“my_field”，Django 在尝试读取/写入该字段时将会失败，因为该表不包含名为“my_field”的列。您通常必须转储整个表并使用 syncdb 重新创建它。我确信您不想这样做，因为您的数据库中已经有一些数据。

假设您想要进行一些更改而不丢失数据。首先，您需要"convert" your app to south .

基本上，当您运行 schemamigration --initial 时，South 将创建一个脚本 (0001_initial.py) 将模型的当前状态复制到数据库中。

如果您通过manage.py migrate reports运行该脚本，它会尝试重新创建您最初拥有的所有表，但在您的情况下，由于您的数据库已经包含这些表，因此它'会对你尖叫说 table 已经存在:

FATAL ERROR - The following SQL query failed: CREATE TABLE "reports_classroom" ("id" integer NOT NULL PRIMARY KEY, "user_id" integer NOT NULL, "added" datetime NOT NULL, "updated" datetime NOT NULL, "name" varchar(30) NOT NULL, "am_or_pm" varchar(2) NOT NULL)
The error was: table "reports_classroom" already exists

要让 South 相信您已经应用了该迁移，请使用 --fake 选项。

manage.py 迁移报告 0001 --fake

这就像说，转到迁移状态 0001_initial(您只需编写名称的数字部分)，但实际上并不应用更改。

完成此操作后，假设您将一个新字段“my_field_02”添加到您的模型之一。和以前一样，Django 引用了模型表中不存在的字段。要在不自己编写 SQL 的情况下创建它，您可以:

manage.py schemamigration reports --auto

这将创建一个名为 0002_auto__add_my_field_02.py 的新迁移，然后您需要通过 manage.py 迁移报告应用该迁移。您也可以说 manage.py migrate reports 0002 来指定您想要转到的迁移状态，但默认情况下 South 将尝试应用以下所有迁移(请记住您已经处于状态 0001) .

我强烈建议您阅读South's documentation并在执行任何操作之前备份您的生产数据。

tl;dr 阅读 this并备份您的数据。