ENH Add configuration to cap report counts for large datasets. (#139)

Opted not to return the result from `getCount()` directly since the PHPDoc says this returns an int (even though it technically already returns a string if the report isn't set up correctly...)

README.md

@@ -20,6 +20,16 @@ The reports section will not show up in the CMS if:
  * There are no reports to show
  * The logged in user does not have permission to view any reports
 
+For large datasets, the reports section may take a long time to load, since each report is getting a count of the items it contains to display next to the title.
+
+To mitigate this issue, there is a cap on the number of items that will be counted per report. This is set at 10,000 items by default, but can be configured using the `limit_count_in_overview` configuration variable. Setting this to `null` will result in showing the actual count regardless of how many items there are.
+
+```yml
+SilverStripe\Reports\Report:
+  limit_count_in_overview: 500
+```
+Note that some reports may have overridden the `getCount` method, and for those reports this may not apply.
+
 ## Links ##
 
  * [License](./LICENSE)

code/Report.php

@@ -25,6 +25,7 @@
 use SilverStripe\ORM\CMSPreviewable;
 use SilverStripe\ORM\DataList;
 use SilverStripe\ORM\DataQuery;
+use SilverStripe\ORM\Limitable;
 use SilverStripe\ORM\SS_List;
 use SilverStripe\Security\Member;
 use SilverStripe\Security\Permission;
@@ -105,6 +106,14 @@ class Report extends ViewableData
         SideReportWrapper::class,
     ];
 
+    /**
+     * The maximum number of items to include in the count in the reports overview
+     *
+     * @config
+     * @var int|null
+     */
+    private static $limit_count_in_overview = 10000;
+
     /**
      * Return the title of this report.
      *
@@ -216,18 +225,46 @@ protected function sanitiseClassName($class)
     /**
      * counts the number of objects returned
      * @param array $params - any parameters for the sourceRecords
+     * @param int|null $limit - the maximum number of records to count
      * @return int
      */
-    public function getCount($params = array())
+    public function getCount($params = array(), $limit = null)
     {
-        $sourceRecords = $this->sourceRecords($params, null, null);
+        $sourceRecords = $this->sourceRecords($params, null, $limit);
         if (!$sourceRecords instanceof SS_List) {
             user_error(static::class . "::sourceRecords does not return an SS_List", E_USER_NOTICE);
             return "-1";
         }
+        // Some reports may not use the $limit parameter in sourceRecords since it isn't actually
+        // used anywhere else - so make sure we limit record counts if possible.
+        if ($sourceRecords instanceof Limitable) {
+            $sourceRecords = $sourceRecords->limit($limit);
+        }
         return $sourceRecords->count();
     }
 
+    /**
+     * Counts the number of objects returned up to a configurable limit.
+     *
+     * Large datasets can cause performance issues for some reports if allowed to count all records.
+     * To mitigate this, you can set the limit_count_in_overview config variable to the maximum number
+     * of items you wish to count to. Counts will be limited to this value, and any counts that hit
+     * this limit will be displayed with a plus, e.g. "500+"
+     *
+     * The default is to have no limit.
+     *
+     * @return string
+     */
+    public function getCountForOverview(): string
+    {
+        $limit = $this->config()->get('limit_count_in_overview');
+        $count = $this->getCount([], $limit);
+        if ($limit && $count == $limit) {
+            $count = "$count+";
+        }
+        return "$count";
+    }
+
     /**
      * Return an array of excluded reports. That is, reports that will not be included in
      * the list of reports in report admin in the CMS.

code/ReportAdmin.php

@@ -242,7 +242,7 @@ public function getEditForm($id = null, $fields = null)
             ));
 
             $columns->setFieldFormatting(array(
-                    'title' => '<a href=\"$Link\" class=\"grid-field__link-block\">$value ($Count)</a>'
+                    'title' => '<a href=\"$Link\" class=\"grid-field__link-block\">$value ($CountForOverview)</a>'
                 ));
             $gridField->addExtraClass('all-reports-gridfield');
             $fields->push($gridField);

tests/ReportTest.php

@@ -114,4 +114,20 @@ public function testColumnLink()
             $titleContent
         );
     }
+
+    public function testCountForOverview()
+    {
+        $report = new ReportTest\FakeTest3();
+
+        // Count is limited to 10000 by default
+        $this->assertEquals('10000+', $report->getCountForOverview());
+
+        // Count is limited as per configuration
+        Config::modify()->set(ReportTest\FakeTest3::class, 'limit_count_in_overview', 15);
+        $this->assertEquals('15+', $report->getCountForOverview());
+
+        // A null limit displays the full count
+        Config::modify()->set(ReportTest\FakeTest3::class, 'limit_count_in_overview', null);
+        $this->assertEquals('15000', $report->getCountForOverview());
+    }
 }

tests/ReportTest/FakeTest3.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace SilverStripe\Reports\Tests\ReportTest;
+
+use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\ArrayList;
+use SilverStripe\Reports\Report;
+
+class FakeTest3 extends Report implements TestOnly
+{
+    public function sourceRecords($params, $sort, $limit)
+    {
+        return new ArrayList(range(1, 15000));
+    }
+}