[wp-trac] [WordPress Trac] #33501: Starting w/ WP4.2, upgrade scenario may fail for non-MySQL installs

[WordPress Trac]

#33501: Starting w/ WP4.2, upgrade scenario may fail for non-MySQL installs
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 Reporter:  RSkoon        |       Owner:
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:
Component:  Database      |     Version:  4.1.2
 Severity:  normal        |  Resolution:
 Keywords:                |     Focuses:
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Comment (by RSkoon):

 Replying to [comment:8 justingreerbbi]:
 > Replying to [comment:6 pento]:
 > > Given that the `is_mysql` flag was created specifically for
 compatibility with non-MySQL db dropins, I'm okay with making some changes
 to how it works in WPDB.
 > >
 > > I think the correct fix would be to change `public $is_mysql = null;`
 to `public $is_mysql = false;`, but I haven't tested that. :-)
 >
 > If we follow suit with is_mysql instances in WP, then simply using
 >
 > {{{
 > if ( empty( $this->is_mysql ) ) {
 >       return false;
 > }
 > }}}
 >
 > would work just right and would also make the checks uniform throughout
 the entire code base. Just for giggles, I am adding a patch.

 [[BR]]
 I think you need both parts of the test...

 Consider the scenario where a DB Drop-in does explicitly set `is_mysql =
 false`...  Then you'll not properly return out of the function because you
 are only testing for empty().

 In that edge case, you would still want this:
 {{{
 if ( false === $this->is_mysql || empty( $this->is_mysql ) ) {
         return false;
 }
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/33501#comment:9>
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