FIX migration task chunking by sorting links by id.

[jcop007]

Description

After running the linkable migration task, not all links were published. This occurs if the number of links exceeds the default chunk limit of 1000 records.

Looking in the database at the LinkField_Link table I could see that some links were published multiple times (2,3) and some links were not published at all, no record in the LinkField_Link_Live table.

The default sort order for links is the "Sort" column which is not unique. I think that when the database was queried for the second chunk the order of results was different. MySQL doesn't guarantee the same order if the sort column isn't unique.

To fix the issue I sorted the results by ID rather than the default sort column. This fixed the issue and all links were published once.

Manual testing steps

Run the link migration task against a database with over 1000 linkable links that need migrating. Afterwards check the LinkField_Link table and the LinkField_Link_Live table to make sure that all links were published once.

Issues

• Not all links are published when running the sheadawson/silverstripe-linkable migration task #367

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[GuySartorelli]

LGTM, thanks