How can I get with fetch() the same results then with fetchAll()? - php

Question

I am selecting data from mySQL database with fetchAll:
$sql = "SELECT id, dateTime, fileName, path, size FROM files WHERE project = ?";
$q = $pdo->prepare($sql);
$q->execute([$id]);
$result = $q->fetchAll(PDO::FETCH_GROUP | PDO::FETCH_UNIQUE | PDO::FETCH_ASSOC);
The array looks like this:
array(2) {
["10002E41F35560F492298F50D14B03A1"]=>
array(5) {
["dateTime"]=>
string(19) "2016-10-12 19:46:25"
["fileName"]=>
string(10) "monkey.jpg"
["path"]=>
string(59) "Volumes/KFS18050001/18050001/elephant/cat/monkey/monkey.jpg"
["size"]=>
string(7) "8650752"
}
["10008A76CEE6BEEEB8000891094A2931"]=>
array(5) {
["dateTime"]=>
string(19) "2016-10-12 14:39:43"
["fileName"]=>
string(9) "horse.jpg"
["path"]=>
string(51) "Volumes/KFS18050001/18050001/elephant/cat/horse.jpg"
["size"]=>
string(7) "8306688"
}
}
But when I have more then 500.000 entries in my database then this is too much for the system. The array is not created. It is loading very long and then I get a blank page. The I tried to use fetch instead of fetchAll:
$sql = "SELECT id, dateTime, fileName, path, size FROM files WHERE project = ?";
$q = $pdo->prepare($sql);
$q->execute([$id]);
$result = $q->fetch(PDO::FETCH_GROUP | PDO::FETCH_UNIQUE | PDO::FETCH_ASSOC);
With fetch, my system can handle the 500.000 entries. But now I do not get the result I need:
array(6) {
["id"]=>
string(32) "10002E41F35560F492298F50D14B03A1"
["dateTime"]=>
string(19) "2016-10-12 19:46:25"
["fileName"]=>
string(10) "monkey.jpg"
["path"]=>
string(59) "Volumes/KFS18050001/18050001/elephant/cat/monkey/monkey.jpg"
["size"]=>
string(7) "8650752"
}
horse.jpg is just not displayed. And the id is now not the key of the array.
Is there any way to retrieve the same result then with fetchAll by using just fetch or is there a way to not overwhelm the system with fetchAll and a lot of entries?

Answer 1

Since I highly doubt you need to load 500,000 images at once, I suggest you try the following.
What I would do is continue using fetchall() but only select the results from the database that you currently need. If you need to load all the images, lets say if you are creating an instagram-type program, I suggest you dynamically load the images and as you scroll down the page, query the database every few hundred images.
You can do this with limit in mysql:
SELECT ....query here.... LIMIT 0,100
and once your user has scrolled down say, 80 images, query the database again with the following:
SELECT ....query here.... LIMIT 100,199
This way you will not overload either the database or the client's system with too many results.