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accesslib: get_user_courses_bycap() is less of a piggy now...
get_user_courses_bycap() replaces get_courses_bycap_fromsess(). Using a combination of in-DB enrolments and in-session capability checks, we narrow down the courses we fetch from the DB for checking. This patch adds a small DB query, and has has a moderate impact on the timings observable on my laptop (~300ms?), but reduces *significantly* the bandwidth used, which in cluster environments with frontends separate from backends has a serious impact.
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martinlanghoff
parent
aeb3916b7a
commit
573674bf47
2 changed files with 94 additions and 22 deletions
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@ -637,8 +637,8 @@ function has_capability_including_child_contexts($context, $capabilitynames) {
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/*
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* Get an array of courses (with magic extra bits)
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* where the access sess data shows that the cap
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* requested is available.
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* where the access sess data and in DB enrolments show
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* that the cap requested is available.
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*
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* The main use is for get_my_courses().
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*
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@ -651,10 +651,24 @@ function has_capability_including_child_contexts($context, $capabilitynames) {
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* - the course records have $c->context which is a fully
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* valid context object. Saves you a query per course!
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*
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* - current implementation is _extremely_ stupid but
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* works fast enough. We can surely do much MUCH better
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* for the common cases, and leave the brute-force to
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* "not-easy-to-narrow-down" cases.
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* - current implementation is split in -
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*
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* - if the user has the cap systemwide, stupidly
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* grab *every* course for a capcheck. This eats
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* a TON of bandwidth, specially on large sites
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* with separate DBs...
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*
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* - otherwise, fetch "likely" courses with a wide net
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* that should get us _cheaply_ at least the courses we need, and some
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* we won't - we get courses that...
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* - are in a category where user has the cap
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* - or where use has a role-assignment (any kind)
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* - or where the course has an override on for this cap
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*
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* - walk the courses recordset checking the caps oneach one
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* the checks are all in memory and quite fast
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* (though we could implement a specialised variant of the
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* has_cap_fromsess() code to speed it up)
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*
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* @param string $capability - name of the capability
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* @param array $sess - access session array
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@ -665,7 +679,7 @@ function has_capability_including_child_contexts($context, $capabilitynames) {
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* @return array $courses - ordered array of course objects - see notes above
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*
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*/
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function get_courses_bycap_fromsess($cap, $sess, $doanything, $sort='c.sortorder ASC', $fields=NULL, $limit=0) {
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function get_user_courses_bycap($userid, $cap, $sess, $doanything, $sort='c.sortorder ASC', $fields=NULL, $limit=0) {
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global $CFG;
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@ -684,19 +698,77 @@ function get_courses_bycap_fromsess($cap, $sess, $doanything, $sort='c.sortorder
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} else {
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$fields = $basefields;
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}
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$coursefields = 'c.' .join(',c.', $fields);
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$sql = "SELECT $coursefields,
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ctx.id AS ctxid, ctx.path AS ctxpath, ctx.depth as ctxdepth
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FROM {$CFG->prefix}course c
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JOIN {$CFG->prefix}context ctx
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ON (c.id=ctx.instanceid AND ctx.contextlevel=".CONTEXT_COURSE.")
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ORDER BY $sort;
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";
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$sysctx = get_context_instance(CONTEXT_SYSTEM);
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if (has_cap_fromsess($cap, $sysctx, $sess, $doanything)) {
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//
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// Apparently the user has the cap sitewide, so walk *every* course
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// (the cap checks are moderately fast, but this moves massive bandwidth w the db)
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// Yuck.
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//
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$sql = "SELECT $coursefields,
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ctx.id AS ctxid, ctx.path AS ctxpath, ctx.depth as ctxdepth
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FROM {$CFG->prefix}course c
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JOIN {$CFG->prefix}context ctx
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ON (c.id=ctx.instanceid AND ctx.contextlevel=".CONTEXT_COURSE.")
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ORDER BY $sort;
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";
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$rs = get_recordset_sql($sql);
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} else {
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//
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// narrow down where we have the caps to a few contexts
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// this will be a combination of
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// - categories where we have the rights
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// - courses where we have an explicit enrolment OR that have an override
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//
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$sql = "SELECT ctx.*
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FROM {$CFG->prefix}context ctx
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WHERE ctx.contextlevel=".CONTEXT_COURSECAT."
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ORDER BY ctx.depth";
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$rs = get_recordset_sql($sql);
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$catpaths = array();
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if ($rs->RecordCount()) {
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while ($catctx = rs_fetch_next_record($rs)) {
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if ($catctx->path != ''
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&& has_cap_fromsess($cap, $catctx, $sess, $doanything)) {
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$catpaths[] = $catctx->path;
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}
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}
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}
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rs_close($rs);
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$catclause = '';
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if (count($catpaths)) {
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$cc = count($catpaths);
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for ($n=0;$n<$cc;$n++) {
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$catpaths[$n] = "ctx.path LIKE '{$catpaths[$n]}/%'";
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}
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$catclause = 'OR (' . join(' OR ', $catpaths) .')';
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}
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unset($catpaths);
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//
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// Note here that we *have* to have the compound clauses
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// in the LEFT OUTER JOIN condition for them to return NULL
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// appropriately and narrow things down...
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//
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$sql = "SELECT $coursefields,
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ctx.id AS ctxid, ctx.path AS ctxpath, ctx.depth as ctxdepth
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FROM {$CFG->prefix}course c
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JOIN {$CFG->prefix}context ctx
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ON (c.id=ctx.instanceid AND ctx.contextlevel=".CONTEXT_COURSE.")
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LEFT OUTER JOIN {$CFG->prefix}role_assignments ra
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ON (ra.contextid=ctx.id AND ra.userid=$userid)
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LEFT OUTER JOIN {$CFG->prefix}role_capabilities rc
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ON (rc.contextid=ctx.id AND rc.capability='$cap')
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WHERE ra.id IS NOT NULL
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OR rc.id IS NOT NULL
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$catclause
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ORDER BY $sort;
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";
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$rs = get_recordset_sql($sql);
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}
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$courses = array();
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$cc = 0; // keep count
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$rs = get_recordset_sql($sql);
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if ($rs->RecordCount()) {
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while ($c = rs_fetch_next_record($rs)) {
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// build the context obj
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@ -585,7 +585,7 @@ function get_courses_page($categoryid="all", $sort="c.sortorder ASC", $fields="c
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* List of courses that a user has access to view. Note that for admins,
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* this usually includes every course on the system.
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*
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* Notes (inherited from get_courses_bycap_fromsess()):
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* Notes (inherited from get_user_courses_bycap()):
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*
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* - $fields is an array of fieldnames to ADD
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* so name the fields you really need, which will
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@ -617,7 +617,7 @@ function get_my_courses($userid, $sort='visible DESC,sortorder ASC', $fields=NUL
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$fields = NULL;
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} else {
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// turn the fields from a string to an array that
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// get_courses_bycap_fromsess() will like...
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// get_user_courses_bycap() will like...
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$fields = explode(',',$fields);
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$fields = array_map('trim', $fields);
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}
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@ -628,9 +628,9 @@ function get_my_courses($userid, $sort='visible DESC,sortorder ASC', $fields=NUL
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} else {
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$accessinfo = get_user_access_sitewide($userid);
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}
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$courses = get_courses_bycap_fromsess('moodle/course:view', $accessinfo,
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$doanything, $sort, $fields,
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$limit);
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$courses = get_user_courses_bycap($userid, 'moodle/course:view', $accessinfo,
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$doanything, $sort, $fields,
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$limit);
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// strangely, get_my_courses() is expected to return the
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// array keyed on id, which messes up the sorting
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$kcourses = array();
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