Use WP_Query or query_posts() or get_posts() for optimizing a site?

Question

I have read other answers, but I don't understand which is more fast (the best and simple for slow server running)?

I have a website with over 1 000 000 hits /day and a slow server with limitations at database connections, so I want to optimise my site.

What do you recommend me to use: WP_Query or query_posts() or get_posts()?

And if I want to show articles in different positions, with different styles can I repeat the function [WP_Query or query_posts() or get_posts()] on every article that I show, or it is best to use it one time and use if $i == 1,2,3 for different styles?

Answer 1

This answer explains the differences. They all use WP_Query, all parameters being equal there is no difference in speed, it's just a question of which is easier for you for your particular needs (hint: it will never be query_posts, which should basically never be used).

You should query the database as few times as possible, so if you can fetch all your posts with a single query, then do some manipulation via php to get the output you need, that is definitely what you should do versus creating multiple queries. Note that a WP_Query object contains some helpful vars to assist in output, like $query_object->post_count and $query_object->current_post.

You should also be employing a cacheing plugin, like W3TC, if server load is an issue.

Answer 2

There's really no need to use query_posts() AT ALL, ever, for any situation.

Why you may be asking?

Simple. Because it instantiates a new WP_Query object and assigns it to the global variable wp_query. And this also explains why using this function jacks with everything else and why you must reset stuff after using it.

Here is the actual query_posts() function

function query_posts($query) {
   $GLOBALS['wp_query'] = new WP_Query();
   return $GLOBALS['wp_query']->query($query);
}

The solution => Just get really good at using the WP_Query object. Practice makes perfect.

If you really want to master this thing, go to wp_includes/query.php file in the WordPress core and just start reading it until you understand the logic of it. It may take a bit, but once you "get" it. Then you'll have it forever.