The posts_pre_query Hook in WPFTS

The posts_pre_query hook in WordPress is a filter that allows modification of WP_Query results before they are returned. WPFTS utilizes this hook in split-query mode (split_the_query) to retrieve complete post data based on their IDs and relevance scores obtained from the initial query.

What WPFTS Does When posts_pre_query is Called:

1. Checking Indexed Search and Split Query Mode: The plugin verifies if indexed search is enabled and split query mode is being used ($wpq->wpftsi_session['use_indexed_search'] and $wpq->wpftsi_session['is_split_query']).

2. Retrieving Complete Post Data: If the conditions are met, WPFTS fetches complete post data from the database using the IDs obtained in the first query. This is done via a separate SQL query to the wp_posts table. The plugin also adds a relev (relevance) field to each post object. Importantly, WPFTS uses a direct SQL query to retrieve data, not the standard get_posts() function, to avoid caching posts without relevance information.

3. Sorting Posts: WPFTS sorts the retrieved posts according to the order defined in the initial query to maintain relevance-based sorting.

Important Functions Involved in posts_pre_query Handling:

• WPFTS_Search::index_posts_pre_query()

• WPFTS_DB::get_results() (for executing the SQL query)

• wpq_set_found_posts (indirectly, for setting found_posts and max_num_pages)

How to Use This in Addon Development:

Addon developers need to understand how WPFTS uses posts_pre_query in split-query mode. If your addon also modifies this filter, ensure your logic doesn’t conflict with WPFTS. Specifically, consider that in this mode, WPFTS completely replaces the standard post array returned by WP_Query with its own.

Additional Notes:

• WPFTS uses posts_pre_query only in split-query mode.

• Split query is used to optimize performance with large search result sets.

• WPFTS sorts posts by relevance while restoring the original order from the first query.