How to recursively get an array of child ids in Modx Revolution without using getChildIds - mysql

Question

getChildIds can be very slow if running it against a large set of resources, so I am trying to write a query and some code to get all the child ids faster.
However I am getting different results from getChildIds & my script.
Can anyone see why these would be yielding different results?
Method using getChildIDs:
$parentDepth = isset($scriptProperties['parentDepth']) ? $scriptProperties['parentDepth'] : 5;
$parents = explode(',', $parents);
$children = array();
foreach ($parents as $parent){
$ids = $modx->getChildIds($parent,10,array('context' => 'web'));
foreach($ids as $id){
$children[] = $id;
}
}
echo ' number of children = ' . count($children);
method using queriees & a loop:
$comma_separated = implode(",", $parents);
$sql = "SELECT `id` from modx_site_content where `parent` IN (".$comma_separated.") and published = 1 and isfolder = 0 and deleted = 0 and hidemenu = 0;";
$results = $modx->query($sql);
$mychildren = array();
while ($row = $results->fetch(PDO::FETCH_ASSOC)) {
$mychildren[] = $row['id'];
}
for($i=0; $i <= 10; $i++){
$comma_separated = implode(",", $mychildren);
$sql = "SELECT `id` from modx_site_content where `parent` IN (".$comma_separated.") and published = 1 and isfolder = 0 and deleted = 0 and hidemenu = 0;";
$results = $modx->query($sql);
while ($row = $results->fetch(PDO::FETCH_ASSOC)) {
$mychildren[] = $row['id'];
}
}
echo ' number of children = ' . count($mychildren);
The getChildIDs method takes nearly 1.5 seconds to run and gives about 1100 results
The SQL/script method runs un under 0.1 second and gives 1700 results.
Either I'm not appending the child ids to the array properly ~or~ maybe getChildIDs is filtering out some other results?
does anyone have any clues as to what could be happening here?

Answer 1

You can try to use built-in method of pdoFetch.
$pdo = $modx->getService('pdoFetch');
$ids = $pdo->getChildIds('modResource', 0);
print_r($ids);
It also recursive, but can be better in some situations.
Of course, you need to install pdoTools from the repository first.

Answer 2

Looking at the code again, the discrepancy in results is pretty obvious now. I'm appending results to the child id array, it's inserting duplicates since one parent can have many children.
the solution to avoid duplicates:
$mychildren[$row['id']] = $row['id'];

Answer 3

getChildIds - is recursive, so it slower by default.