varange on "slow-queries with many posts. what is this sql SELECT doing?"

Hi all, I get heaps of slow-query logs (set to 2s at the moment) from this type of query:

SELECT l.ID, post_title, post_content, post_name, post_author, post_parent, post_modified_gmt, post_date, post_date_gmt
FROM (

SELECT ID
FROM wp_posts
WHERE post_status =  'publish'
AND post_password =  ''
AND post_type =  'post'
AND post_author !=0
AND post_date !=  '0000-00-00 00:00:00'
ORDER BY post_modified ASC
LIMIT 100
OFFSET 108700
)o
JOIN wp_posts l ON l.ID = o.ID
ORDER BY l.ID

What is this query doing? Is it a related-posts thing? What can I do to speed it up? My wp-posts table has over 300k entries now.

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