xadmin importexport插件使用過程出現的問題記錄

1、要安裝django-import-export版本，並將此應用註冊到

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'apps.devices.apps.DevicesConfig',
    'xadmin',
    'crispy_forms',
    'envs',
    'assets',
    'meeting',
    'terminals',
    'import_export',
]

2、使用的tablib to 0.12.1版本，否則會出現導入csv時報錯‘Error encountered while trying to read file: test.csv’

Problem
Error encountered while trying to read file CSV with python 2.7 #957

Solution
Downgrade tablib to 0.12.1

Acceptance Criteria
Doc updated with good dependencies

 

3、導入時報錯：    "This is forbidden when an 'atomic' block is active."
TransactionManagementError: This is forbidden when an 'atomic' block is active.

原因分析：詳見https://github.com/django-import-export/django-import-export/issues/609

This is because import_export.resource.Resource.import_data() tests for connection.features.supports_transaction. This is OK on most RDBMS, but on MySQL the support for transactions depends on the database engine being used, so Django runs a test to see if the DB supports transactions. During the test, a temporary table is created and also calls set_autocommit(False). That call can only be executed outside of an atomic block (Django code test for in_atomic_block for the DB connection).

This also has the side effect the table created by Django (called ROLLBACK_TEST) to test transaction support is never deleted from the DB, because the rollback to the savepoint marked by Django is never performed.

I'll submit a Pull Request with a short patch to prevent this: if the import_data() is running inside an atomic block, then we know the DB supports transactions and we don't test for connection.features.supports_transaction.

解決辦法：

將import_export/resources.py 的

supports_transactions = getattr(connection.features, "supports_transactions", False)

改爲：
supports_transactions = getattr(connection, 'in_atomic_block', False) or getattr(connection.features, "supports_transactions", False)

4、爲了控制在導入預覽頁面展示的內容條數，增加以下優化：

當導入數據量行數很大時，預覽所有數據意義不大。
（1）找到路徑：xadmin\plugins\importexport(xadmin包源碼）
大概在156行處，可以找到ImportView視圖；
再往下，在234行處：

result = resource.import_data(dataset, dry_run=True,
                              raise_errors=False,
                              file_name=import_file.name,
                              user=request.user)
context['result'] = result
後面增加：
if len(result.rows) < 20:
    result_display = result.rows
else:
    result_display = result.rows[:20]
context['result_display'] = result_display

context[‘result_display’]就是通過TemplateResponse傳給模板展示預覽數據。
（2）修改模板
找到路徑：templates/xadmin/import_export/import.html(xadmin包源碼）
在大約99行位置，
將{% for row in result.rows %}改成{% for row in result_display %}