Why doesn't wp search find everything?

Question

WordPress

Hello !
I did a search on the wp website (the topic is my own)
Here is a link to the form files:
https://drive.google.com/open?id=1w-KXqOQf0KolQOKv...
Question:
the search is not looking for everything, but specifically, they are looking for only records, and pages and custom entries are not looking, what's the problem?
PS How can I do it WITHOUT plugins!!!
Thank you )

Answer 1

Because WP doesn't know how to search for custom types.
If without plugins, then put hooks in functions.php and search as needed:

add_filter('posts_join', ...);
add_filter('posts_where', ...);
add_filter('posts_groupby', ...);