[wp-trac] [WordPress Trac] #48078: Some WP_XXX_Query::query() methods produce incorrect results when called in a loop

[WordPress Trac]

#48078: Some WP_XXX_Query::query() methods produce incorrect results when called in
a loop
--------------------------+-----------------------------
 Reporter:  pbiron        |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  General       |    Version:
 Severity:  normal        |   Keywords:  2nd-opinion
  Focuses:  multisite     |
--------------------------+-----------------------------
 While testing a
 [https://core.trac.wordpress.org/attachment/ticket/37392/37392.9.patch
 patch] for #37392 I came across what ''may'' be a bug in
 `WP_Site_Query::query()`.

 That patch creates a `WP_Site_Query` object and then in a loop does
 various different `query()`'s, as in:

 {{{#!php
 $q = new WP_Site_Query();
 $args   = array(
         'network_id'    => $network_id,
         'number'        => 1,
         'fields'        => 'ids',
         'no_found_rows' => false,
 );

 foreach ( array( 'public', 'archived', ... ) as $status ) {
         $_args = $args;
         $_args[ $status ] = 1;

         $q->query( $_args );
         // do something with the results of this site query.
 }
 }}}

 However, calling `query()` in a loop like that doesn't produce the
 expected results other than the 1st time through the loop.

 Why?  Because when `query()` calls `WP_Site_Query::get_site_ids()` on
 subsequent iterations, the protected class member `$sql_clauses` still has
 its value from the previous iteration through the loop and the "new" query
 basically gets added to the previous queries.

 In the case of the above code this results in the query for `archive = 1`
 to actually be `public = 1 AND archive = 1` which is **not** what is
 intended.

 Looking at other `WP_XXX_Query()` classes, I ''think'' the following
 suffer from the same thing (although I haven't written code to test that):

 1. `WP_Network_Query`
 2. `WP_Term_Query`

 but the following do **not**:

 1. `WP_Query` (because it doesn't use a class member for the clauses)
 2. `WP_User_Query` (because it uses a `prepare_query( $query )` method
 which resets the class member(s))

 So, I guess the question is: should these `query()` methods be expected to
 work when called multiple times in a loop (with different queries each
 time) or is that **not** an intended use?

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/48078>
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