Ticket #47642: patch.47642.20220204.1

Index: src/wp-includes/class-wp-query.php
===================================================================
--- src/wp-includes/class-wp-query.php  (revision 52673)
+++ src/wp-includes/class-wp-query.php  (working copy)
@@ -2367,7 +2367,24 @@
                        } else {
                                $q['orderby'] = urldecode( $q['orderby'] );
                                $q['orderby'] = addslashes_gpc( $q['orderby'] );
-
+                               
+                // https://core.trac.wordpress.org/ticket/47642
+                // Database engine fix to prevent strange (duplicate or missing) results in paginated resultsets
+                // Adds the unique ID primary key if needed
+                $do_not_force_ID = array( 'ID', 'rand', 'relevance' );
+                if ( is_array( $q['orderby'] ) ) {
+                    if( count( array_intersect_key( $q['orderby'], $do_not_force_ID ) ) == 0 ) {
+                        // No match found so we need to add our unique ID here
+                        $q['orderby']['ID'] = 'ASC';
+                    }
+                } else {
+                        // Not an array, test as string
+                        if( !in_array( $q['orderby'], $do_not_force_ID )  ) {
+                            // No match found so we need to add our unique ID here, note the space
+                            $q['orderby'] .= ' ID';
+                        }
+                }
+                
                                foreach ( explode( ' ', $q['orderby'] ) as $i => $orderby ) {
                                        $parsed = $this->parse_orderby( $orderby );
                                        // Only allow certain values for safety.