I'm working now on high performance Wordpress website and it requires me to analyze a lot of queries, caching options etc. I've discovered that if you use
get_the_post_thumbnail() even within the loop, then WordPress makes a query for every post's thumbnail url.
So if you've got your page set to display 25 posts with thumbnails, it makes 25 additional queries to retrieve image URL.
get_the_post_thumbnail() I'm reducing query number from 49 to 4. A big number. However, thumbnails are really needed for this theme.
Do you know if there's any way to include post thumbnail URL in the post object by default?