Should duplicate values be removed from mysql IN clause?

[NotionCommotion]

I had been using the following script, but question whether I should bother as MySQL will not return duplicates.  Is it better to just send MySQL everything, and let it deal with it?

$input=[5,3,null,7,5,3,2];
if($input=array_values(array_filter(array_unique($input)))){  //Remove non-unique values, null values, and reorder
    $list=rtrim(str_repeat('?,',count($input)),',');
    $sql="SELECT a,b,c FROM my_table WHERE id IN ($list)"; //my_table.id has a NOT NULL constraint
    $stmt = $this->db->prepare($sql);
    $stmt->execute($input);
}

[requinix]

If the list has only constant values then it will be sorted and MySQL will do a binary search (->). That's one additional comparison every time you double the size of the list.

 

While not a big difference, I'd remove them: one pass in PHP to remove vs. however-many additional comparisons in MySQL.