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Merged from MOODLE_14_STABLE moodle--eduforge--1.3.3--patch-222 - SQL improvements\n Better SQL performance for get_courses() and get_courses_page() calls, specially from the categories page. This gives much better performance when browsing existing courses

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martinlanghoff
2004-11-18 02:31:53 +00:00
parent 2171c83396
commit 6315b1c8b6
1 changed files with 79 additions and 106 deletions
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lib/datalib.php
+79 -106
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@@ -1955,134 +1955,107 @@ function get_site () {
}
/**
* Returns list of courses, for whole site, or category
*
* @uses $CFG
* @uses $USER
* @param int $categoryid ?
* @param string $sort ?
* @param string $fields A comma separated list of fields to be returned from the chosen table.
* @return array An array of {@link $COURSE} records
* @todo Finish documenting this function
*/
function get_courses($categoryid='all', $sort='c.sortorder ASC', $fields='c.*') {
/// This function deliberately uses PHP to do the checking at the end,
/// because MySQL has been known to really bog down when trying to do a JOIN
/// on the 'course' and 'user_teachers' table at the same time.
* Returns list of courses, for whole site, or category
*
* Returns list of courses, for whole site, or category
*
* @param type description
*
* Important: Using c.* for fields is extremely expensive because
* we are using distinct. You almost _NEVER_ need all the fields
* in such a large SELECT
*/
function get_courses($categoryid="all", $sort="c.sortorder ASC", $fields="c.*") {
global $USER, $CFG;
$select = array();
if ($categoryid != 'all') {
$select[] = "c.category = '$categoryid'";
$categoryselect = "";
if ($categoryid != "all" && is_numeric($categoryid)) {
$categoryselect = "c.category = '$categoryid'";
}
/// Admins can always see invisible courses
/// Creators can always see invisible courses
/// Teachers can only see their own invisible courses <- needs detailed checking
/// Students can't see invisible courses at all
/// Guests can't see invisible courses at all
$visiblecourses = '';
$showallinvisible = iscreator(); // includes admins
$hideallinvisible = empty($USER->id) || (!isteacher());
if ($hideallinvisible) {
$select[] = 'c.visible > 0';
$teachertable = "";
$visiblecourses = "";
$sqland = "";
if (!empty($categoryselect)) {
$sqland = "AND ";
}
if ($select) {
$selectsql = $CFG->prefix .'course c WHERE '. implode(' AND ', $select);
} else {
$selectsql = $CFG->prefix .'course c ';
}
$courses = get_records_sql('SELECT '. $fields .' FROM '. $selectsql .' ORDER BY '. $sort);
if ($courses and (!$hideallinvisible) and (!$showallinvisible)) { // For ordinary users we need to check visibility
foreach ($courses as $key => $course) {
if ($course->visible == 0) { // Invisible course, let's check if we are a teacher
if (!isteacher($course->id)) { // We shouldn't see this
unset($courses[$key]);
}
}
if (!empty($USER->id)) { // May need to check they are a teacher
if (!iscreator()) {
$visiblecourses = "$sqland ((c.visible > 0) OR t.userid = '$USER->id')";
$teachertable = "LEFT JOIN {$CFG->prefix}user_teachers t ON t.course = c.id";
}
} else {
$visiblecourses = "$sqland c.visible > 0";
}
return $courses;
if ($categoryselect or $visiblecourses) {
$selectsql = "{$CFG->prefix}course c $teachertable WHERE $categoryselect $visiblecourses";
} else {
$selectsql = "{$CFG->prefix}course c $teachertable";
}
return get_records_sql("SELECT ".((!empty($teachertable)) ? " DISTINCT " : "")." $fields FROM $selectsql ".((!empty($sort)) ? "ORDER BY $sort" : ""));
}
/**
* Returns list of courses, for whole site, or category
*
* Similar to get_courses, but allows paging
*
* @uses $CFG
* @uses $USER
* @param int $categoryid ?
* @param string $sort ?
* @param string $fields A comma separated list of fields to be returned from the chosen table.
* @param int $totalcount Passed by reference. ?
* @param int $limitfrom ?
* @param int $limitnum ?
* @return array An array of {@link $COURSE} records
* @todo Finish documenting this function
*/
function get_courses_page($categoryid='all', $sort='c.sortorder ASC', $fields='c.*',
&$totalcount, $limitfrom='', $limitnum='') {
/// This function deliberately uses PHP to do the checking at the end,
/// because MySQL has been known to really bog down when trying to do a JOIN
/// on the 'course' and 'user_teachers' table at the same time.
/**
* Returns list of courses, for whole site, or category
*
* Similar to get_courses, but allows paging
*
* @param type description
*
* Important: Using c.* for fields is extremely expensive because
* we are using distinct. You almost _NEVER_ need all the fields
* in such a large SELECT
*/
function get_courses_page($categoryid="all", $sort="c.sortorder ASC", $fields="c.*",
&$totalcount, $limitfrom="", $limitnum="") {
global $USER, $CFG;
$select = array();
if ($categoryid != 'all') {
$select[] = 'c.category = \''. $categoryid .'\'';
$categoryselect = "";
if ($categoryid != "all") {
$categoryselect = "c.category = '$categoryid'";
}
/// Admins can always see invisible courses
/// Creators can always see invisible courses
/// Teachers can only see their own invisible courses <- needs detailed checking
/// Students can't see invisible courses at all
/// Guests can't see invisible courses at all
$visiblecourses = '';
$showallinvisible = iscreator(); // includes admins
$hideallinvisible = empty($USER->id) || (!isteacher());
if ($hideallinvisible) {
$select[] = 'c.visible > 0';
$teachertable = "";
$visiblecourses = "";
$sqland = "";
if (!empty($categoryselect)) {
$sqland = "AND ";
}
if ($select) {
$selectsql = $CFG->prefix .'course c WHERE '.implode(' AND ', $select);
} else {
$selectsql = $CFG->prefix .'course c ';
}
$courses = get_records_sql('SELECT '. $fields .' FROM '. $selectsql .' ORDER BY '. $sort);
if ($courses and (!$hideallinvisible) and (!$showallinvisible)) { // For ordinary users we need to check visibility
foreach ($courses as $key => $course) {
if ($course->visible == 0) { // Invisible course, let's check if we are a teacher
if (!isteacher($course->id)) { // We shouldn't see this
unset($courses[$key]);
}
}
if (!empty($USER)) { // May need to check they are a teacher
if (!iscreator()) {
$visiblecourses = "$sqland ((c.visible > 0) OR t.userid = '$USER->id')";
$teachertable = "LEFT JOIN {$CFG->prefix}user_teachers t ON t.course=c.id";
}
} else {
$visiblecourses = "$sqland c.visible > 0";
}
$totalcount = count($courses);
if ($courses and ($limitfrom or $limitnum)) {
$courses = array_slice($courses, (int)$limitfrom, (int)$limitnum);
if ($limitfrom !== "") {
switch ($CFG->dbtype) {
case "mysql":
$limit = "LIMIT $limitfrom,$limitnum";
break;
case "postgres7":
$limit = "LIMIT $limitnum OFFSET $limitfrom";
break;
default:
$limit = "LIMIT $limitnum,$limitfrom";
}
} else {
$limit = "";
}
return $courses;
$selectsql = "{$CFG->prefix}course c $teachertable WHERE $categoryselect $visiblecourses";
$totalcount = count_records_sql("SELECT COUNT(DISTINCT c.id) FROM $selectsql");
return get_records_sql("SELECT DISTINCT $fields FROM $selectsql ".((!empty($sort)) ? "ORDER BY $sort" : "")." $limit");
}