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MDL-30185 question engine reporting: add redundant where to query for perf.

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Without this, MySQL fails to cope.
This commit is contained in:
Tim Hunt
2011-11-15 11:00:55 +00:00
parent e25ecdfcf3
commit 471992218f
2 changed files with 44 additions and 27 deletions
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question/engine/datalib.php
+35 -26
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@@ -865,33 +865,42 @@ ORDER BY
END) = 0";
}
public function question_attempt_latest_state_view($alias) {
return "(
SELECT
{$alias}qa.id AS questionattemptid,
{$alias}qa.questionusageid,
{$alias}qa.slot,
{$alias}qa.behaviour,
{$alias}qa.questionid,
{$alias}qa.variant,
{$alias}qa.maxmark,
{$alias}qa.minfraction,
{$alias}qa.flagged,
{$alias}qa.questionsummary,
{$alias}qa.rightanswer,
{$alias}qa.responsesummary,
{$alias}qa.timemodified,
{$alias}qas.id AS attemptstepid,
{$alias}qas.sequencenumber,
{$alias}qas.state,
{$alias}qas.fraction,
{$alias}qas.timecreated,
{$alias}qas.userid
/**
* Get a subquery that returns the latest step of every qa in some qubas.
* Currently, this is only used by the quiz reports. See
* {@link quiz_attempt_report_table::add_latest_state_join()}.
* @param string $alias alias to use for this inline-view.
* @param qubaid_condition $qubaids restriction on which question_usages we
* are interested in. This is important for performance.
* @return array with two elements, the SQL fragment and any params requried.
*/
public function question_attempt_latest_state_view($alias, qubaid_condition $qubaids) {
return array("(
SELECT {$alias}qa.id AS questionattemptid,
{$alias}qa.questionusageid,
{$alias}qa.slot,
{$alias}qa.behaviour,
{$alias}qa.questionid,
{$alias}qa.variant,
{$alias}qa.maxmark,
{$alias}qa.minfraction,
{$alias}qa.flagged,
{$alias}qa.questionsummary,
{$alias}qa.rightanswer,
{$alias}qa.responsesummary,
{$alias}qa.timemodified,
{$alias}qas.id AS attemptstepid,
{$alias}qas.sequencenumber,
{$alias}qas.state,
{$alias}qas.fraction,
{$alias}qas.timecreated,
{$alias}qas.userid
FROM {question_attempts} {$alias}qa
JOIN {question_attempt_steps} {$alias}qas ON
{$alias}qas.id = {$this->latest_step_for_qa_subquery($alias . 'qa.id')}
) $alias";
FROM {$qubaids->from_question_attempts($alias . 'qa')}
JOIN {question_attempt_steps} {$alias}qas ON
{$alias}qas.id = {$this->latest_step_for_qa_subquery($alias . 'qa.id')}
WHERE {$qubaids->where()}
) $alias", $qubaids->from_where_params());
}
protected function latest_step_for_qa_subquery($questionattemptid = 'qa.id') {