Removed double left join on posts_join_filter

[rebeccahum]

As per #417, I have removed the double left join on posts_join_filter.

[trepmal]

In my test, which may not be comprehensive, I'm not seeing a change in the SQL query.

My test query:

$query_args = [
	'post_type'      => 'post',
	'post_status'    => 'publish',
	'posts_per_page' => 10,
	'author_name'    => $curauth->user_nicename,
	'tax_query'      => [
		[
			'taxonomy' => 'category',
			'field'    => 'slug',
			'terms'    => $category_slug,
		]
	],
	'orderby' => 'date',
	'order'   => 'DESC'
];

$featured_posts_author = new WP_Query( $query_args );

builds sql:

/* pre-patch */
SELECT SQL_CALC_FOUND_ROWS  wp_posts.ID FROM wp_posts
  LEFT JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id)
  LEFT JOIN wp_term_relationships AS tr1 ON (wp_posts.ID = tr1.object_id)
  LEFT JOIN wp_term_taxonomy ON ( tr1.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id ) WHERE 1=1  AND (
  wp_term_relationships.term_taxonomy_id IN (4)
) AND (( (wp_term_taxonomy.taxonomy = 'author' AND wp_term_taxonomy.term_id = '5') OR (wp_term_taxonomy.taxonomy = 'author' AND wp_term_taxonomy.term_id = '2'))) AND wp_posts.post_type = 'post' AND ((wp_posts.post_status = 'publish')) GROUP BY wp_posts.ID HAVING MAX( IF ( wp_term_taxonomy.taxonomy = 'author', IF (  wp_term_taxonomy.term_id = '5' OR  wp_term_taxonomy.term_id = '2',2,1 ),0 ) ) <> 1  ORDER BY wp_posts.post_date DESC LIMIT 0, 10

/* with patch */
SELECT SQL_CALC_FOUND_ROWS  wp_posts.ID FROM wp_posts
  LEFT JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id)
  LEFT JOIN wp_term_relationships AS tr1 ON (wp_posts.ID = tr1.object_id)
  LEFT JOIN wp_term_taxonomy ON ( tr1.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id ) WHERE 1=1  AND (
  wp_term_relationships.term_taxonomy_id IN (4)
) AND (( (wp_term_taxonomy.taxonomy = 'author' AND wp_term_taxonomy.term_id = '5') OR (wp_term_taxonomy.taxonomy = 'author' AND wp_term_taxonomy.term_id = '2'))) AND wp_posts.post_type = 'post' AND ((wp_posts.post_status = 'publish')) GROUP BY wp_posts.ID HAVING MAX( IF ( wp_term_taxonomy.taxonomy = 'author', IF (  wp_term_taxonomy.term_id = '5' OR  wp_term_taxonomy.term_id = '2',2,1 ),0 ) ) <> 1  ORDER BY wp_posts.post_date DESC LIMIT 0, 10

I might have missed something though, if you have a better test query let me know

[trepmal]

Looks like it was just me bumbling around juggling too many queries...

I ran 3 sets of queries: (a) author + tax_query, (b) just author, and (c) just tax_query

pre and post patch, a and c are identical 👍

for b here's before

SELECT SQL_CALC_FOUND_ROWS  wp_posts.ID FROM wp_posts
LEFT JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id)
LEFT JOIN wp_term_relationships AS tr1 ON (wp_posts.ID = tr1.object_id)
LEFT JOIN wp_term_taxonomy ON ( tr1.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id )
 WHERE 1=1  AND ((wp_posts.post_author = 3 OR (wp_term_taxonomy.taxonomy = 'author' AND wp_term_taxonomy.term_id = '6'))) AND wp_posts.post_type = 'post' AND ((wp_posts.post_status = 'publish')) GROUP BY wp_posts.ID HAVING MAX( IF ( wp_term_taxonomy.taxonomy = 'author', IF (  wp_term_taxonomy.term_id = '6',2,1 ),0 ) ) <> 1  ORDER BY wp_posts.post_date DESC LIMIT 0, 10

and after

SELECT SQL_CALC_FOUND_ROWS  wp_posts.ID FROM wp_posts
LEFT JOIN wp_term_relationships AS tr1 ON (wp_posts.ID = tr1.object_id)
LEFT JOIN wp_term_taxonomy ON ( tr1.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id )
 WHERE 1=1  AND ((wp_posts.post_author = 3 OR (wp_term_taxonomy.taxonomy = 'author' AND wp_term_taxonomy.term_id = '6'))) AND wp_posts.post_type = 'post' AND ((wp_posts.post_status = 'publish')) GROUP BY wp_posts.ID HAVING MAX( IF ( wp_term_taxonomy.taxonomy = 'author', IF (  wp_term_taxonomy.term_id = '6',2,1 ),0 ) ) <> 1  ORDER BY wp_posts.post_date DESC LIMIT 0, 10

Which is just a noisy way of saying it looks good!

edit: before/after examples accidentally reversed 🤦‍♀️

[catchmyfame]

@rebeccahum @trepmal Please see #508 with regard to the SQL changes