标签：io ar os 使用 sp for on 文件 数据
django>=1.7数据库迁移只有三个命令
migrate，用来迁移数据库。
用法：migrate app
makemigrations，用来检测数据库变更和生成数据库迁移文件。
用法：makemigratioins app
sqlmigrate，用来把数据库迁移文件转换成数据库语言(displays the SQL statements for a migratioin.）
用法：sqlmigrate app migration，比如makemigrations生成了0001_initial.py，就用sqlmigrate app 0001_intial，这里0001_initial就是migration参数。
一般如果某次migration使用sqlmigrate没有提示错误，那么在migrate时就能成功。
migrate成功例子：
root@kanfangha:~/redguy# python manage.py migrate accost Operations to perform: Apply all migrations: accost Running migrations: Applying accost.0002_auto_20141212_1327... OK
如果是失败：
Operations to perform: Apply all migrations: accost Running migrations: Applying accost.0002_auto_20141212_1327... FAKED
所以如果migrate失败了，可以用sqlmigrate调试。
比如：
root@kanfangha:~/redguy# python manage.py sqlmigrate accost 0002_auto_20141212_1323 Traceback (most recent call last): File "manage.py", line 10, in <module> execute_from_command_line(sys.argv) File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line utility.execute() File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 288, in run_from_argv self.execute(*args, **options.__dict__) File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/sqlmigrate.py", line 30, in execute return super(Command, self).execute(*args, **options) File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 338, in execute output = self.handle(*args, **options) File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/sqlmigrate.py", line 61, in handle sql_statements = executor.collect_sql(plan) File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 77, in collect_sql migration.apply(project_state, schema_editor, collect_sql=True) File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 107, in apply operation.database_forwards(self.app_label, schema_editor, project_state, new_state) File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 139, in database_forwards schema_editor.alter_field(from_model, from_field, to_field) File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 470, in alter_field new_field, ValueError: Cannot alter field accost.Accost.like into accost.Accost.like - they are not compatible types (you cannot alter to or from M2M fields, or add or remove through= on M2M fields)
上面提示说不能将accost.Accost.like alter为一个M2M(ManyToMany)fields，这种情况，把字段like换个名字就行了，换成likes。然后在执行sqlmigrate就成功。
如下：
root@kanfangha:~/redguy# python manage.py sqlmigrate accost 0002_auto_20141212_1327
BEGIN;
ALTER TABLE "accost_accost" DROP COLUMN "collected" CASCADE;
ALTER TABLE "accost_accost" DROP COLUMN "like" CASCADE;
CREATE TABLE "accost_accost_collects" ("id" serial NOT NULL PRIMARY KEY, "accost_id" integer NOT NULL, "myuser_id" integer NOT NULL, UNIQUE ("accost_id", "myuser_id"));
CREATE TABLE "accost_accost_likes" ("id" serial NOT NULL PRIMARY KEY, "accost_id" integer NOT NULL, "myuser_id" integer NOT NULL, UNIQUE ("accost_id", "myuser_id"));
CREATE INDEX accost_accost_collects_372770c0 ON "accost_accost_collects" ("accost_id");
ALTER TABLE "accost_accost_collects" ADD CONSTRAINT "accost_accost_co_accost_id_2b66c74632ab3db8_fk_accost_accost_id" FOREIGN KEY ("accost_id") REFERENCES "accost_accost" ("id") DEFERRABLE INITIALLY DEFERRED;
CREATE INDEX accost_accost_collects_8b14fb18 ON "accost_accost_collects" ("myuser_id");
ALTER TABLE "accost_accost_collects" ADD CONSTRAINT "accost_accost__myuser_id_1bf115233bc10d70_fk_accounts_myuser_id" FOREIGN KEY ("myuser_id") REFERENCES "accounts_myuser" ("id") DEFERRABLE INITIALLY DEFERRED;
CREATE INDEX accost_accost_likes_372770c0 ON "accost_accost_likes" ("accost_id");
ALTER TABLE "accost_accost_likes" ADD CONSTRAINT "accost_accost_li_accost_id_3700c980b7e22204_fk_accost_accost_id" FOREIGN KEY ("accost_id") REFERENCES "accost_accost" ("id") DEFERRABLE INITIALLY DEFERRED;
CREATE INDEX accost_accost_likes_8b14fb18 ON "accost_accost_likes" ("myuser_id");
ALTER TABLE "accost_accost_likes" ADD CONSTRAINT "accost_accost__myuser_id_6af76a97d74d7ca4_fk_accounts_myuser_id" FOREIGN KEY ("myuser_id") REFERENCES "accounts_myuser" ("id") DEFERRABLE INITIALLY DEFERRED;
COMMIT;
标签：io ar os 使用 sp for on 文件 数据
原文地址：http://my.oschina.net/u/862582/blog/355421
