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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 02:31:11 +00:00
parent ee99d4dd14
commit ea9d7e8815
1 changed files with 58 additions and 72 deletions
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lib/datalib.php
+58 -72
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@@ -1752,53 +1752,44 @@ function get_site () {
* 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.*") {
/// 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.
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
$teachertable = "";
$visiblecourses = "";
$showallinvisible = iscreator(); // includes admins
$hideallinvisible = empty($USER->id) || (!isteacher());
if ($hideallinvisible) {
$select[] = "c.visible > 0";
$sqland = "";
if (!empty($categoryselect)) {
$sqland = "AND ";
}
if (!empty($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";
}
if ($select) {
$selectsql = "{$CFG->prefix}course c WHERE ".implode(' AND ', $select);
if ($categoryselect or $visiblecourses) {
$selectsql = "{$CFG->prefix}course c $teachertable WHERE $categoryselect $visiblecourses";
} else {
$selectsql = "{$CFG->prefix}course c ";
$selectsql = "{$CFG->prefix}course c $teachertable";
}
$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]);
}
}
}
}
return $courses;
return get_records_sql("SELECT ".((!empty($teachertable)) ? " DISTINCT " : "")." $fields FROM $selectsql ".((!empty($sort)) ? "ORDER BY $sort" : ""));
}
@@ -1810,61 +1801,56 @@ function get_courses($categoryid="all", $sort="c.sortorder ASC", $fields="c.*")
* Similar to get_courses, but allows paging
*
* @param type description
*
* Important: Using c.* for fields is extremely expensive because
* we are using distinct. You almost _NEVER_ need all the fields
* in such a large SELECT
*/
function get_courses_page($categoryid="all", $sort="c.sortorder ASC", $fields="c.*",
&$totalcount, $limitfrom="", $limitnum="") {
/// 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.
global $USER, $CFG;
$select = array();
$categoryselect = "";
if ($categoryid != "all") {
$select[] = "c.category = '$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
$teachertable = "";
$visiblecourses = "";
$showallinvisible = iscreator(); // includes admins
$hideallinvisible = empty($USER->id) || (!isteacher());
if ($hideallinvisible) {
$select[] = "c.visible > 0";
$sqland = "";
if (!empty($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");
}