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⚡ Optimize admin question loading (Fix N+1 query) #14

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⚡ Optimize admin question loading (Fix N+1 query) #14

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29 changes: 25 additions & 4 deletions quiz_system_git/admin.php
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Original file line number Diff line number Diff line change
Expand Up @@ -250,7 +250,29 @@

$m_display_ID = 1;

while($m_row = $stmt->fetch()){
$questions = $stmt->fetchAll(PDO::FETCH_ASSOC);

// Collect IDs
$questionIDs = [];
foreach ($questions as $q) {
$questionIDs[] = $q['question_id'];
}

// Batch fetch answers
$answersByQuestion = [];
if (!empty($questionIDs)) {
$chunks = array_chunk($questionIDs, 500);
foreach ($chunks as $chunk) {
$placeholders = implode(',', array_fill(0, count($chunk), '?'));
$stmtAns = $pdo->prepare("SELECT * FROM answers WHERE question_id IN ($placeholders)");
$stmtAns->execute($chunk);
while ($row = $stmtAns->fetch(PDO::FETCH_ASSOC)) {
$answersByQuestion[$row['question_id']][] = $row;
}
}
}

foreach ($questions as $m_row){
$m_answers='';
//id var = id column and so on
$m_id = $m_row['id'];
Expand Down Expand Up @@ -296,16 +318,15 @@
}

//gathering answers of question here
$stmtAns = $pdo->prepare("SELECT * FROM answers WHERE question_id=:questionID");
$stmtAns->execute(['questionID' => $m_question_id]);
$currentAnswers = isset($answersByQuestion[$m_question_id]) ? $answersByQuestion[$m_question_id] : [];

$m_answers .= '<tr>
<td></td>
<td>
<ol type="a">
';

while($m_row2 = $stmtAns->fetch()){
foreach ($currentAnswers as $m_row2){
//putting column values in variables
$m_answer = $m_row2['answer'];
$m_correct = $m_row2['correct'];
Expand Down