# HG changeset patch
# User Mads Kiilerich <madski@unity3d.com>
# Date 1469716489 -7200
# Node ID 190cb30841de32c6d54516ebdb18ab969377499a
# Parent  6b723a49a9a1f9590e8585f6c418eb25f3ee0fe5
branches: fix performance of branch selectors with many branches - only show the first 200 results

The way we use select2, it will cause browser performance problems when a
select list contains thousands of entries. The primary bottleneck is the DOM
creation, secondarily for the query to filter through the entries and decide
what to show. We thus primarily have to limit how many entries we put in the
drop-down, secondarily limit the iteration over data.

One tricky case is where the user specifies a short but full branch name (like
'trunk') but many other branches contains the same string (not necessarily at
the beginning, like 'for-trunk-next-week') which come before the perfect match
in the branch list. It is thus not a solution to just stop searching when a
fixed amount of matches have been found.

Instead, we limit the amount of ordinary query matches, but always show all
prefix matches. We thus always have to iterate through all entries, but we
start using the (presumably) cheaper prefix search when the limit has been
reached.

There is no filtering initially when there is no query term, so that case has
to be handled specially.

Upstream select2 is now at 4.x. Upgrading is not trivial, and getting this
fixed properly upstream is not a short term solution. Instead, we customize our
copy. The benefit from this patch is bigger than the overhead of "maintaining"
it locally.

diff -r 6b723a49a9a1 -r 190cb30841de kallithea/public/js/select2/select2.js
--- a/kallithea/public/js/select2/select2.js	Fri Aug 12 03:13:59 2016 +0200
+++ b/kallithea/public/js/select2/select2.js	Thu Jul 28 16:34:49 2016 +0200
@@ -1097,7 +1097,13 @@
 
                         // collect the created nodes for bulk append
                         var nodes = [];
-                        for (i = 0, l = results.length; i < l; i = i + 1) {
+
+                        // Kallithea customization: maxResults
+                        l = results.length;
+                        if (query.term.length == 0 && l > opts.maxResults) {
+                            l = opts.maxResults;
+                        }
+                        for (i = 0; i < l; i = i + 1) {
 
                             result=results[i];
 
@@ -1138,6 +1144,10 @@
                             nodes.push(node[0]);
                         }
 
+                        if (results.length >= opts.maxResults) {
+                            nodes.push($('<li class="select2-no-results"><div class="select2-result-label">Too many matches found</div></li>'));
+                        }
+
                         // bulk append the created nodes
                         container.append(nodes);
                         liveRegion.text(opts.formatMatches(results.length));
@@ -1161,16 +1171,25 @@
 
             if (select) {
                 opts.query = this.bind(function (query) {
+                    // Kallithea customization: maxResults
                     var data = { results: [], more: false },
                         term = query.term,
-                        children, placeholderOption, process;
+                        children, placeholderOption, process,
+                        maxResults = opts.maxResults || -1,
+                        termLower = term.toLowerCase();
 
                     process=function(element, collection) {
                         var group;
                         if (element.is("option")) {
+                          if (collection.length < maxResults) {
                             if (query.matcher(term, element.text(), element)) {
                                 collection.push(self.optionToData(element));
                             }
+                          } else {
+                            if (element.text().toLowerCase().indexOf(termLower) == 0) {
+                                collection.push(self.optionToData(element));
+                            }
+                          }
                         } else if (element.is("optgroup")) {
                             group=self.optionToData(element);
                             element.children().each2(function(i, elm) { process(elm, group.children); });
diff -r 6b723a49a9a1 -r 190cb30841de kallithea/templates/changelog/changelog.html
--- a/kallithea/templates/changelog/changelog.html	Fri Aug 12 03:13:59 2016 +0200
+++ b/kallithea/templates/changelog/changelog.html	Thu Jul 28 16:34:49 2016 +0200
@@ -308,7 +308,7 @@
                 // change branch filter
                 $("#branch_filter").select2({
                     dropdownAutoWidth: true,
-                    minimumInputLength: 1,
+                    maxResults: 50,
                     sortResults: branchSort
                     });
 
diff -r 6b723a49a9a1 -r 190cb30841de kallithea/templates/files/files.html
--- a/kallithea/templates/files/files.html	Fri Aug 12 03:13:59 2016 +0200
+++ b/kallithea/templates/files/files.html	Thu Jul 28 16:34:49 2016 +0200
@@ -233,7 +233,7 @@
     // change branch filter
     $("#branch_selector").select2({
         dropdownAutoWidth: true,
-        minimumInputLength: 1,
+        maxResults: 50,
         sortResults: branchSort
         });
 
diff -r 6b723a49a9a1 -r 190cb30841de kallithea/templates/pullrequests/pullrequest.html
--- a/kallithea/templates/pullrequests/pullrequest.html	Fri Aug 12 03:13:59 2016 +0200
+++ b/kallithea/templates/pullrequests/pullrequest.html	Thu Jul 28 16:34:49 2016 +0200
@@ -202,6 +202,7 @@
 
       $("#org_ref").select2({
           dropdownAutoWidth: true,
+          maxResults: 50,
           sortResults: branchSort
       });
       $("#org_ref").on("change", function(e){
@@ -217,6 +218,7 @@
 
       $("#other_ref").select2({
           dropdownAutoWidth: true,
+          maxResults: 50,
           sortResults: branchSort
       });
       $("#other_ref").on("change", function(e){