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MDL-79639 quiz_statistics: Prevent database deadlocks

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This changes the cache purge code to select IDs for deletion
first, rather than using a subquery in a DELETE, since this
risks causing a deadlock in MySQL.
This commit is contained in:
Mark Johnson
2023-10-19 08:58:07 +01:00
parent ce43783c16
commit 6a9e714c97
1 changed files with 15 additions and 9 deletions
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question/classes/statistics/responses/analysis_for_question.php
+15 -9
View File
@@ -208,15 +208,21 @@ class analysis_for_question {
$transaction = $DB->start_delegated_transaction();
$DB->delete_records_select('question_response_count',
'analysisid IN (
SELECT id
FROM {question_response_analysis}
WHERE hashcode= ? AND whichtries = ? AND questionid = ?
)', [$qubaids->get_hash_code(), $whichtries, $questionid]);
$DB->delete_records('question_response_analysis',
['hashcode' => $qubaids->get_hash_code(), 'whichtries' => $whichtries, 'questionid' => $questionid]);
$analysisids = $DB->get_fieldset_select(
'question_response_analysis',
'id',
'hashcode = ? AND whichtries = ? AND questionid = ?',
[
$qubaids->get_hash_code(),
$whichtries,
$questionid,
]
);
if (!empty($analysisids)) {
[$insql, $params] = $DB->get_in_or_equal($analysisids);
$DB->delete_records_select('question_response_count', 'analysisid ' . $insql, $params);
$DB->delete_records_select('question_response_analysis', 'id ' . $insql, $params);
}
foreach ($this->get_variant_nos() as $variantno) {
foreach ($this->get_subpart_ids($variantno) as $subpartid) {