[wp-trac] [WordPress Trac] #36748: Updating tables to utf8mb4 causes some columns to change type unexpectedly

[WordPress Trac]

#36748: Updating tables to utf8mb4 causes some columns to change type unexpectedly
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 Reporter:  tollmanz                      |       Owner:
     Type:  defect (bug)                  |      Status:  new
 Priority:  normal                        |   Milestone:  4.5.2
Component:  Upgrade/Install               |     Version:  4.2
 Severity:  normal                        |  Resolution:
 Keywords:  needs-patch needs-unit-tests  |     Focuses:  performance
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Changes (by pento):

 * keywords:   => needs-patch needs-unit-tests
 * focuses:   => performance
 * milestone:  Awaiting Review => 4.5.2


Comment:

 I'm inclined to fix this by preventing `dbDelta()` from downgrading the
 size of a `*text` (or `*blob`) field.

 We're already allowing for custom sized columns in the WPDB preflight
 checks, so this is mostly about preventing an unnecessary `ALTER TABLE`.

 Because of the significant performance implications, this will need to be
 backported to the 4.2 branch, in preparation for major release auto
 updates.

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Ticket URL: <https://core.trac.wordpress.org/ticket/36748#comment:1>
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