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Fix for performance issues of regrading data update on huge data sets #150

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Merged
ndunand merged 1 commit into from
Jun 3, 2026
Merged

Fix for performance issues of regrading data update on huge data sets #150

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32 changes: 19 additions & 13 deletions classes/db/stepdata_migration_utils.php
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Original file line number Diff line number Diff line change
Expand Up @@ -70,14 +70,16 @@ public static function to_new_name(
return qtype_matrix_question::responsekey($newrowindex, $newcolindex);
}

public static function stepdata_sql(string $qinsql, string $stepdatanamelike): string {
public static function stepdata_sql(int $minqid, int $maxqid, string $stepdatanamelike): string {
$operator = str_contains($stepdatanamelike, '%') ? 'LIKE' : '=';
return "SELECT qasd.id as stepdataid, q.id as questionid, qa.id as attemptid, qas.id as stepid, qasd.name, qasd.value
FROM {question} q
JOIN {question_attempts} qa ON qa.questionid = q.id
JOIN {question_attempt_steps} qas ON qas.questionattemptid = qa.id
JOIN {question_attempt_step_data} qasd ON qasd.attemptstepid = qas.id
WHERE qasd.name LIKE '" . $stepdatanamelike . "'
AND q.id " . $qinsql . "
WHERE qasd.name ".$operator." '" . $stepdatanamelike . "'
AND q.qtype = 'matrix'
AND q.id BETWEEN ".$minqid." AND ".$maxqid."
ORDER BY qasd.id
";
}
Expand All @@ -87,7 +89,7 @@ public static function extract_matrixinfos(array $questionids):array {

$matrixinfos = [];

[$qinsql, $qidparams] = $DB->get_in_or_equal(array_keys($questionids));
[$qinsql, $qidparams] = $DB->get_in_or_equal($questionids);
// Leave out matrix questions with broken data (missing col records)
$colssql = "
SELECT qmc.id as colid, qm.id as matrixid, q.id as questionid
Expand Down Expand Up @@ -119,9 +121,10 @@ public static function extract_matrixinfos(array $questionids):array {
$matrixcols->close();

// Collect info about attempt row order.
$orderstepdatasql = stepdata_migration_utils::stepdata_sql($qinsql, '_order');
// FIXME: Should probably be done in batches of 100.000
$orderdatars = $DB->get_recordset_sql($orderstepdatasql, $qidparams);
$minqid = min($questionids);
$maxqid = max($questionids);
$orderstepdatasql = stepdata_migration_utils::stepdata_sql($minqid, $maxqid, '_order');
$orderdatars = $DB->get_recordset_sql($orderstepdatasql);
foreach ($orderdatars as $orderdata) {
if (!$orderdata->questionid || !isset($matrixinfos[$orderdata->questionid])) {
continue;
Expand All @@ -137,12 +140,14 @@ public static function extract_matrixinfos(array $questionids):array {

public static function migrate_stepdata(array &$matrixinfos, array $questionids):void {
global $DB;
[$qinsql, $qidparams] = $DB->get_in_or_equal(array_keys($questionids));
$cellstepdatasql = self::stepdata_sql($qinsql, 'cell%');
// FIXME: Should probably be done in batches of 100.000

$celldataupdatechunksize = 10000;
$celldatars = $DB->get_recordset_sql($cellstepdatasql, $qidparams);
$minqid = min($questionids);
$maxqid = max($questionids);
$cellstepdatasql = self::stepdata_sql($minqid, $maxqid, 'cell%');

// Lower update chunks lead to lower times for the update query.
// This seems to be caused by using lots of CASE statements.
$celldataupdatechunksize = 100;
$celldatars = $DB->get_recordset_sql($cellstepdatasql);
$nrprocessedchunkcelldata = 0;
$celldataids = [];
$sqlnamecase = '';
Expand Down Expand Up @@ -190,5 +195,6 @@ public static function migrate_stepdata(array &$matrixinfos, array $questionids)
}
}
$celldatars->close();
unset($celldatars);
}
}
15 changes: 11 additions & 4 deletions db/upgrade.php
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Original file line number Diff line number Diff line change
Expand Up @@ -162,22 +162,29 @@ function xmldb_qtype_matrix_upgrade(int $oldversion): bool {
if ($total) {
core_php_time_limit::raise();
// Ensure we have a base memory limit with which to work.
// This should at least amount to 2GB RAM for this process.
raise_memory_limit(MEMORY_HUGE);
$now = time();
// Guessed batch size for processing questions when updating question attempt step data.
$questionbatchsize = 1000;
// Batch size for processing questions when updating question attempt step data.
// The given batch size led to 1.4 GB of the process being matrixinfos.
// This was deemed okay because the recordsets do not take much memory.
$questionbatchsize = 25000;
// Show a progress bar.
$pbar = new progress_bar('upgrade_qtype_matrix_stepdata_to_row', 500, true);
$offset = 0;
while ($offset < $total) {
$pbar->update($offset, $total, "Updating attempt data for qtype_matrix questions - $offset/$total questions.");
$questionids = $DB->get_records(
$questionids = array_keys($DB->get_records(
'question', ['qtype' => 'matrix'], 'id ASC', 'id', $offset, $questionbatchsize
);
));
$offset += $questionbatchsize;
$matrixinfos = stepdata_migration_utils::extract_matrixinfos($questionids);
// Now migrate the cell stepdata for the question batch (also done in batches).
stepdata_migration_utils::migrate_stepdata($matrixinfos, $questionids);
// Necessary to prevent out of memory errors because PHP didn't garbage collect early enough.
unset($matrixinfos);
gc_collect_cycles();
gc_mem_caches();
}
$pbar->update($offset, $total, 'Done. Seconds: '.(time() - $now));
}
Expand Down
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