_find_post_by_old_slug() │ WP 4.9.3

Core function that retrieves the post ID for redirecting from the old url to the new one.

Used in the function wp_old_slug_redirect(), which performs the redirect if the post ID was found.

Algorithm:

Creates the basis for the SQL query to find the post ID by the given post type and the specified value in the meta-field with the key _wp_old_slug equal to get_query_var('name').
Adds clarifications to the query based on get_query_var('year'), get_query_var('monthnum'), get_query_var('day'), if the permalink of the post uses the year, month, day of publication.
Using $wpdb->get_var() makes the query and returns the post ID.

Internal function — this function is designed to be used by the kernel itself. It is not recommended to use this function in your code.

Used By: wp_old_slug_redirect()

1 time — 0.000494 sec (fast) | 50000 times — 17.66 sec (slow) | PHP 7.2.5, WP 4.9.8

No Hooks.

Returns

int. post ID.

Usage

_find_post_by_old_slug( $post_type );

$post_type(string) (required): The current post type based on query variables.

Examples

#1 An example from the WordPress core

See the code of function wp_old_slug_redirect().

Notes

See: wp_old_slug_redirect()

Global. wpdb. $wpdb WordPress database abstraction object.

Changelog

Since 4.9.3

Introduced.

`_find_post_by_old_slug() find post by old slug` code ^{WP 7.1.2}

wp-includes/query.php

function _find_post_by_old_slug( $post_type ) {
	global $wpdb;

	$query = $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta, $wpdb->posts WHERE ID = post_id AND post_type = %s AND meta_key = '_wp_old_slug' AND meta_value = %s", $post_type, get_query_var( 'name' ) );

	/*
	 * If year, monthnum, or day have been specified, make our query more precise
	 * just in case there are multiple identical _wp_old_slug values.
	 */
	if ( get_query_var( 'year' ) ) {
		$query .= $wpdb->prepare( ' AND YEAR(post_date) = %d', get_query_var( 'year' ) );
	}
	if ( get_query_var( 'monthnum' ) ) {
		$query .= $wpdb->prepare( ' AND MONTH(post_date) = %d', get_query_var( 'monthnum' ) );
	}
	if ( get_query_var( 'day' ) ) {
		$query .= $wpdb->prepare( ' AND DAYOFMONTH(post_date) = %d', get_query_var( 'day' ) );
	}

	$key          = md5( $query );
	$last_changed = wp_cache_get_last_changed( 'posts' );
	$cache_key    = "find_post_by_old_slug:$key";
	$cache        = wp_cache_get_salted( $cache_key, 'post-queries', $last_changed );
	if ( false !== $cache ) {
		$id = $cache;
	} else {
		$id = (int) $wpdb->get_var( $query );
		wp_cache_set_salted( $cache_key, $id, 'post-queries', $last_changed );
	}

	return $id;
}