In data migration tool config file we have<bulk_size> and <direct_document_copy> elements. What values are expected for these tags and what are their purpose?


1 Answer 1



It is the amount of data processed at one time.

Set bulk_size as 0 and it will be auto-detected for every document. It is better than set bulk_size as a fixed value.


Default value is 0, set it as 1 for better performance.

Set direct_document_copy as 1 will direct copy data from database, but 'source' and 'destination' databases MUST be placed on the same MySQL instance and 'destination' user MUST be granted with 'SELECT' permissions on 'source' database.

  • 1
    auto-detected for every document. What is it mean ? Can you please explain ?
    – Aji
    Feb 11, 2020 at 12:58
  • @Aji It means the value is decided by the migration module codes. How it works and decide value you need to study its codes, I don't spend much time on the auto-detected value, because there is a lot of other migration works to do. I just set bulk_size as 0 and it works well. Migration is a big deal, we don’t need to make every principle clear when using tools, that's a terrible workload. If anyone has time to study the codes, could add a new answer here :)
    – Key Shang
    Jun 15, 2020 at 4:31

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