如果数据未正确加载到维度/事实表中，我需要执行哪些步骤来清理数据

Question

假设有一个场景，有一个数据加载到事实表\\维表的过程，经过分析发现有1亿条记录被错误加载，我需要执行哪些步骤才能正确清理数据。

Answer 1

Here are two practices which help in that scenario:

1. Take a backup or snapshot before each batch. In the case of a major error like this you can roll back to the snapshot, reload and process the correct data.

2. Maintain an insert-only persistent staging area in the DW, such as a data vault, with each row stamped with a batch ID and timestamp. Remove the rows in error, and rebuild your facts and dimensions.

If this represents a real situation your only chance is #1.

If you don't have a reliable backup, and you have updated and/or deleted rows during the ETL/ELT process, you don't have any record of the pre-fail state and it may be impossible to go back.