I’m new to the “posts_” filter hooks and wanted to know a few things from those in the know:
In this question, someone posted an answer using posts_join that took a second parameter of $query:
add_filter('posts_join',array(&$this,'posts_join'),10,2);
...
function posts_join($join,$query) {
}
Is this an instance of wp_query or something similar?
Same example:
How would I determine the post type so that I can do custom joins for each custom post type I have on the admin side
What does the posts_fields filter hook do? from the example I’ve seen, it looks like it replaces the columns in the SELECT clause of an SQL call.
Am I correct in that assumption, and does it too have more parameters that can be called??
I find some examples but I can’t get any solid documentation anywhere.
When you use one of the methods to query for posts (
query_posts(),get_posts()orWP_Queryobject) arguments you provide are processed and turned into SQL query. This happens inWP_Query->&get_posts()method.Since arguments are not omnipotent there are a lot of hooks in there that allow to modify or override parts of resulting SQL query.
posts_joinis part of query that handles SQL JOINs – adding additional tables to the mix, for example tables related to taxonomies when they are needed.posts_fieldsseem to control which database fields will be returned in query, it seems to default to all fields frompoststable.