[wp-trac] [WordPress Trac] #18210: Update_post_meta is case insensitive on meta_key, but get_post_meta is NOT

[WordPress Trac]

#18210: Update_post_meta is case insensitive on meta_key, but get_post_meta is NOT
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 Reporter:  anmari                               |       Owner:
     Type:  defect (bug)                         |      Status:  new
 Priority:  normal                               |   Milestone:  Awaiting
Component:  Database                             |  Review
 Severity:  normal                               |     Version:  3.2
 Keywords:  dev-feedback needs-patch needs-      |  Resolution:
  unit-tests                                     |     Focuses:
                                                 |  performance
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Comment (by webaware):

 I ran into a related problem with user meta. A client used a CSV importer
 and accidentally capitalised the first letter of a meta key. Because case
 insensitivity in MySQL, but case sensitivity in the WP user meta PHP code,
 the billing last name would never load "for some users". Fixed with this
 query, and a flush of the object cache:

 {{{
 update wp_usermeta
 set meta_key = 'billing_last_name'
 where meta_key collate utf8mb4_bin = 'Billing_last_name'
 }}}

 FWIW, I ran the query below on one of my testbed sites with over 200
 plugins (multisite, lots of compatibility testing) and didn't find any
 examples of plugins having user meta keys with capital letters.

 {{{
 select distinct meta_key
 from wp_usermeta
 where meta_key collate utf8mb4_bin regexp '[A-Z]'
 }}}

 Post meta is a different story, however; meta keys are sometimes directly
 used on the front end, and thus may legitimately contain capital letters.

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Ticket URL: <https://core.trac.wordpress.org/ticket/18210#comment:10>
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