Alternative to query_posts for main loop?

Possible Duplicate:
When to use WP_query(), query_posts() and pre_get_posts

I just noticed today that the documentation for query_posts() mentions some “disadvantages” of using query_posts for altering the main Loop, notably: ’causes additional SQL queries’.

This seems to imply that there’s another way / a better way. Obviously there’s get_posts() and WP_Query for secondary loops, but I don’t see them as addressing the “disadvantages” listed in the Codex documentation.

I can see that by waiting until you’re in the template to run query_posts, WordPress has already run a query once and this is now a second query that clobbers the first one (the first one being basically ignored). This definitely DOES sound inefficient (though perhaps not a big deal, who knows?)

My question is: is there an alternative to query_posts that does NOT add “additional SQL queries” or is the Codex documentation simply deceiving?

Answers:

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Method 1

When I added the drawbacks to the Codex, I was mainly thinking of using the ‘request’ filter as an alternative to query_posts().

That filter is only run for the main query, so that solves the problem with ‘pre_get_posts’, which fires for every query.

The downside is that you don’t have access to query flags like is_single() etc.

Here’s one way you could get access to them, without actually doing the SQL queries:

function alter_the_query( $request ) {
    $dummy_query = new WP_Query();  // the query isn't run if we don't pass any query vars
    $dummy_query->parse_query( $request );

    // this is the actual manipulation; do whatever you need here
    if ( $dummy_query->is_home() )
        $request['category_name'] = 'news';

    return $request;
}
add_filter( 'request', 'alter_the_query' );

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