Opened 8 years ago
Last modified 6 years ago
#39273 new defect (bug)
Updating to 4.7 can break serialized data because $wpdb->determine_charset now forces utf8 when DB_CHARSET is set to utf8mb4
| Reported by: |
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Owned by: | |
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| Milestone: | Awaiting Review | Priority: | normal |
| Severity: | normal | Version: | 4.7 |
| Component: | Database | Keywords: | dev-feedback |
| Focuses: | Cc: |
Description
I've seen this happen several times now. DB_CHARSET is defined as utf8mb4 and the columns in the database are set to utf8mb4_unicode_ci. However, the changes in 38581 are now forcing utf8 causing the serialized array lengths to change when the data is queried and breaking them because the charsets don't match.
I can't say for certain because I'm debugging this issue on a site that isn't mine, but I don't think anyone explicitly set DB_CHARSET to utf8mb4 in wp-config.php. It appears that at one point, WordPress set that define and created (or updated) those tables to utf8mb4_unicode_ci.
Deleting the DB_CHARSET define fixes the issue but that doesn't seem like an ideal solution for users who update and end up with a broken site.
I'll admit this is a bit over my head, so I'm hoping someone smarter than me might be able to chime in with some more info :) I'm definitely available to keep the conversation going. Thanks!