[wp-trac] [WordPress Trac] #30681: Using a value in a meta_query (in WP_Query) combined with EXISTS OR NOT EXISTS breaks query

[WordPress Trac]

#30681: Using a value in a meta_query (in WP_Query) combined with EXISTS OR NOT
EXISTS breaks query
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 Reporter:  barrykooij    |       Owner:
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  4.1
Component:  General       |     Version:  trunk
 Severity:  normal        |  Resolution:
 Keywords:                |     Focuses:
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Changes (by barrykooij):

 * keywords:  has-patch needs-unit-tests =>
 * component:  Query => General


Comment:

 The reason it breaks:

 In the switch statement on $meta_compare the default case will be used for
 EXISTS and NOT EXISTS. Therefor this code will run on an empty string
 {{{
 $where = $wpdb->prepare( '%s', $meta_value );
 }}}

 resulting in '' ( a string with just 2 quotes). That string with just 2
 quotes will pass this check
 {{{
 if ( $where ) {
 }}}
 and therefor attach the complete where statement to the SQL chunks.

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Ticket URL: <https://core.trac.wordpress.org/ticket/30681#comment:2>
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