Improve performance of `get_page_children()`.

The new algorithm uses a hash table rather than function recursion, reducing
complexity to O(N). On large numbers of pages, the performance improvement is
several orders of magnitude.

Props santagada, hailin, mihai.
Fixes #10852.

git-svn-id: https://develop.svn.wordpress.org/trunk@32355 602fd350-edb4-49c9-b593-d223f7449a82
This commit is contained in:
Boone Gorges 2015-05-05 19:36:58 +00:00
parent ba712c6789
commit bb29a878c6
1 changed files with 24 additions and 11 deletions

View File

@ -4317,25 +4317,38 @@ function get_page_by_title( $page_title, $output = OBJECT, $post_type = 'page' )
}
/**
* Retrieve child pages from list of pages matching page ID.
* Identify descendants of a given page ID in a list of page objects.
*
* Matches against the pages parameter against the page ID. Also matches all
* children for the same to retrieve all children of a page. Does not make any
* SQL queries to get the children.
* Descendants are identified from the `$pages` array passed to the function. No database queries are performed.
*
* @since 1.5.1
*
* @param int $page_id Page ID.
* @param array $pages List of pages' objects.
* @param int $page_id Page ID.
* @param array $pages List of page objects from which descendants should be identified.
* @return array List of page children.
*/
function get_page_children( $page_id, $pages ) {
$page_list = array();
// Build a hash of ID -> children.
$children = array();
foreach ( (array) $pages as $page ) {
if ( $page->post_parent == $page_id ) {
$page_list[] = $page;
if ( $children = get_page_children( $page->ID, $pages ) ) {
$page_list = array_merge( $page_list, $children );
$children[ intval( $page->post_parent ) ][] = $page;
}
$page_list = array();
// Start the search by looking at immediate children.
if ( isset( $children[ $page_id ] ) ) {
// Always start at the end of the stack in order to preserve original `$pages` order.
$to_look = array_reverse( $children[ $page_id ] );
while ( $to_look ) {
$p = array_pop( $to_look );
$page_list[] = $p;
if ( isset( $children[ $p->ID ] ) ) {
foreach ( array_reverse( $children[ $p->ID ] ) as $child ) {
// Append to the `$to_look` stack to descend the tree.
$to_look[] = $child;
}
}
}
}