--- apachesolr_stats.info
+++ apachesolr_stats.info
@@ -0,0 +1,6 @@
+; $Id$
+name = Apache Solr statistics
+description = Keeps and reports statistics about Apache Solr usage and performance.
+dependencies[] = apachesolr
+package = Apache Solr
+core = "6.x"

--- apachesolr_stats.install
+++ apachesolr_stats.install
@@ -0,0 +1,130 @@
+<?php
+// $Id$
+
+
+/**
+ * Implementation of hook_install().
+ */
+function apachesolr_stats_install() {
+  drupal_install_schema('apachesolr_stats');
+}
+
+/**
+ * Implementation of hook_uninstall().
+ */
+function apachesolr_stats_uninstall() {
+  // Remove tables.
+  drupal_uninstall_schema('apachesolr_stats');
+}
+
+/**
+ * Implementation of hook_enable().
+ */
+ /*
+function apachesolr_XXXXX_enable() {
+  drupal_set_message(t('All existing Organic Group posts will be re-indexed'), 'warning');
+  db_query("UPDATE {apachesolr_search_node} SET changed = %d WHERE nid IN (SELECT nid FROM {og_ancestry})", time());
+}
+*/
+
+/**
+ * Implementation of hook_schema().
+ */
+function apachesolr_stats_schema() {
+  $schema['apachesolr_stats'] = array(
+    'description' => t('Table that contains a log of Apache Solr queries and performace.'),
+    'fields' => array(
+      'qid' => array(
+        'type' => 'serial',
+        'not null' => TRUE,
+        'description' => 'Primary Key: Unique log ID.',
+      ),
+      'timestamp' => array(
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => 'Unix timestamp of when query occurred.',
+      ),
+      'numfound' => array(
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => 'Number of results.',
+      ),
+      'total_time' => array(
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => 'Total query time (miliseconds).',
+      ),
+      'prepare_time' => array(
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => 'Time taken by Solr prepare phase for this query (miliseconds).',
+      ),
+      'process_time' => array(
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => 'Time taken by Solr process phase for this query (miliseconds).',
+      ),
+      'uid' => array(
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => 'The {users}.uid of the user who triggered the query.',
+      ),
+      'sid' => array(
+        'type' => 'varchar',
+        'length' => 64,
+        'not null' => TRUE,
+        'default' => '',
+        'description' => 'Session ID of user who triggered the query.',
+      ),
+      'showed_suggestions' => array(
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => 'Indicates whether a spelling suggestion was shown.',
+      ),
+      'page' => array(
+        'type' => 'varchar',
+        'length' => 10,
+        'not null' => TRUE,
+        'default' => '',
+        'description' => 'Current results page.',
+      ),
+      'keywords' => array(
+        'type' => 'varchar',
+        'length' => 128,
+        'not null' => TRUE,
+        'default' => '',
+        'description' => 'Query keywords arguments.',
+      ),
+      'filters' => array(
+        'type' => 'varchar',
+        'length' => 128,
+        'not null' => TRUE,
+        'default' => '',
+        'description' => 'Query filter arguments.',
+      ),
+      'sort' => array(
+        'type' => 'varchar',
+        'length' => 128,
+        'not null' => TRUE,
+        'default' => '',
+        'description' => 'Query sort arguments.',
+      ),
+      'params' => array(
+        'type' => 'text',
+        'not null' => TRUE,
+        'size' => 'big',
+        'description' => "Query object's complete parameters.",
+      ),
+    ),
+    'primary key' => array('qid'),
+  );
+
+  return $schema;
+}

--- apachesolr_stats.module
+++ apachesolr_stats.module
@@ -0,0 +1,304 @@
+<?php
+// $Id$
+
+/**
+ * @file
+ *   Keeps and reports statistics about Apache Solr usage and performance.
+ *
+ * TODO:
+ *   - Track clickthrus on results, on facets, on spelling suggestions, etc. to
+ *      determine "value" of facets (e.g. Facet X has % clickthru rate)
+ *   - The report itself.
+ */
+
+/**
+ * Implementation of hook_menu().
+ */
+function apachesolr_stats_menu() {
+  return array(
+    'admin/settings/apachesolr/stats' => array(
+      'title'            => 'Statistics',
+      'description'      => 'Apache Solr Statistics settings to measure usage and performance.',
+      'page callback'    => 'drupal_get_form',
+      'page arguments'   => array('apachesolr_stats_admin'),
+      'access arguments' => array('administer search'),
+    ),
+    'admin/reports/apachesolr/stats' => array(
+      'title'            => 'Statistics',
+      'description'      => 'Report of Apache Solr usage and performance.',
+      'page callback'    => 'apachesolr_stats_report',
+      'page arguments'   => array(),
+      'access arguments' => array('administer search'),
+    ),
+  );
+}
+
+/**
+ * Build a settings form.
+ */
+function apachesolr_stats_admin() {
+  $form = array();
+  $options = array('1' => t('Enabled'), '0' => t('Disabled'));
+  $form['access'] = array(
+    '#type' => 'fieldset',
+    '#title' => t('Apache Solr query log settings'));
+  $form['access']['apachesolr_stats_enabled'] = array(
+    '#type' => 'radios',
+    '#title' => t('Enable access log'),
+    '#default_value' => variable_get('apachesolr_stats_enabled', 0),
+    '#options' => $options,
+    '#description' => t('Log each query to Apache Solr.'));
+  $period = drupal_map_assoc(array(3600, 10800, 21600, 32400, 43200, 86400, 172800, 259200, 604800, 1209600, 2419200, 4838400, 9676800), 'format_interval');
+  $form['access']['apachesolr_stats_flush_log_timer'] = array(
+    '#type' => 'select',
+    '#title' => t('Discard query logs older than'),
+    '#default_value'   => variable_get('apachesolr_stats_flush_log_timer', 259200),
+    '#options' => $period,
+    '#description' => t('Older query log entries will be automatically discarded. (Requires a correctly configured <a href="@cron">cron maintenance task</a>.)', array('@cron' => url('admin/reports/status'))));
+
+  $form = system_settings_form($form);
+  return $form;
+}
+
+/**
+ * Implementation of hook_apachesolr_modify_query().
+ */
+function apachesolr_stats_apachesolr_modify_query(&$query, &$params, $caller) {
+  if (variable_get('apachesolr_stats_enabled', 0)) {
+    // Add the debug query argument. See: http://wiki.apache.org/solr/CommonQueryParameters#head-f45a9396425956a4db8d6478ed6029adfb7b0858
+    if ($caller == 'apachesolr_search') {
+      $params['debugQuery'] = 'true';
+    }
+  }
+}
+
+/**
+ * Implementation of apachesolr_stats_apachesolr_process_results().
+ */
+function apachesolr_stats_apachesolr_process_results(&$results) {
+  if (!variable_get('apachesolr_stats_enabled', 0)) {
+    return;
+  }
+  
+  global $user;
+  $response = apachesolr_static_response_cache();
+  $query = apachesolr_current_query();
+  $url_queryvalues = $query->get_url_queryvalues();
+  
+  db_query("INSERT INTO {apachesolr_stats}
+    (timestamp, uid, sid, numfound, showed_suggestions, total_time, prepare_time, process_time, page, keywords, filters, sort, params)
+    VALUES
+    (%d, %d, '%s', %d, %d, %d, %d, %d, '%s', '%s','%s','%s','%s')",
+    time(),
+    $user->uid,
+    $user->sid,
+    $response->response->numFound,
+    (int) get_object_vars($response->spellcheck->suggestions),
+    $response->debug->timing->time,
+    $response->debug->timing->prepare->time,
+    $response->debug->timing->process->time,
+    isset($_GET['page']) ? $_GET['page'] : '',
+    $query->get_query_basic(),
+    $url_queryvalues['filters'],
+    $url_queryvalues['sort'],
+    serialize($response->responseHeader->params));
+
+  return;
+    
+  /*
+  $times = array();
+  $times['total']['total'] = $response->debug->timing->time;
+  foreach (array('prepare', 'process') as $phase) {
+    foreach($response->debug->timing->prepare as $key => $value) {
+      if (is_object($value)) {
+        $times[$phase][$key] = (int) $value->time;
+      } else {
+        $times[$phase]['total'] = (int) $value;
+      }
+    }
+  }
+  dsm($times);
+  return;
+  */
+}
+
+/**
+ * Callback for admin/reports/apachesolr/stats.
+ *
+ * TODO: Hardcoded to display queries per minute; this will very likely break with large logfiles.
+ */
+function apachesolr_stats_report() {  
+  if (! variable_get('apachesolr_stats_enabled', 0)) {
+    return t('Logging is disabled in the !link. Enable it to log Apache Solr queries.', array('!link' => l('module configuration page', 'admin/settings/apachesolr/stats')));
+  }
+
+  // Decide what granularity to use: minute, hour or day
+  $g = "minute";
+  $granularities = array(
+    'minute' => array(
+      'name' => t('minute'),
+      'div' => 60,
+    ),
+    'hour' => array(
+      'name' => t('hour'),
+      'div' => 60*60,
+    ),
+   'day' => array(
+      'name' => t('day'),
+      'div' => 60*60*24,
+    ),
+  );
+  $granularity = $granularities[$g];
+
+  // Process log
+  $suggestions = 0;
+  $queries = 0;
+  $users = array();
+  $sessions = array();
+  $result = db_query_range("SELECT * FROM {apachesolr_stats} ORDER BY timestamp DESC", 0, 5000);
+  $start_timeslot = 0;
+  $last_timeslot = 0;
+  while ($record = db_fetch_object($result)) {
+    $timeslot = intval($record->timestamp / $granularity['div']);
+    if ($last_timeslot == 0) { $last_timeslot = $timeslot; }
+    $users[$record->uid]++;
+    $sessions[$record->sid]++;
+    if ($record->suggestions) {
+      $suggestions++;
+    }
+    $total_queries++;
+    $time['total'] += $record->total_time;
+    $time['prepare'] += $record->prepare_time;
+    $time['process'] += $record->process_time;
+
+    #dsm($record->
+    // Field usage; only when on first results page (meaning it's a fresh search)
+    if ($record->page == "") {
+      if (trim($record->keywords) != "") {
+        $field_usage['keyword']++;
+      }
+      foreach (explode(' ', $record->filters) as $filter) {
+        list($fieldname, $value) = explode(':', $filter);
+        if ($fieldname) {
+          $field_usage[$fieldname]++;
+        }
+      }
+    }
+
+    // Group some stats into timeslots (minutes, hours) to show trends
+    if (empty($user_slot[$record->uid][$timeslot])) {
+      $data_per_granularity['users_per_slot'][$timeslot]++;
+      $user_slot[$record->uid][$timeslot] = TRUE;
+    }
+    $data_per_granularity['queries'][$timeslot]++;
+    $count_per_granularity[$timeslot]++;
+    $data_per_granularity['total_time'][$timeslot] += $record->total_time;
+  }
+  $start_timeslot = $timeslot;
+  #dsm($queries_per_granularity);
+
+  if (sizeof($sessions) == 0 || sizeof($users) == 0 || $total_queries == 0) {
+    return t('There are no logged queries yet.');
+  }
+
+  $s[t('Queries')] = $total_queries;
+  $s[t('Spellchecker suggestions')] = $suggestions;
+  $s[t('Sessions')] = sizeof($sessions);
+  $s[t('Unique users')] = sizeof($users);
+  $s[t('Average queries per user')] = sprintf("%.1f", $total_queries / sizeof($users));
+  $s[t('Average queries per session')] = sprintf("%.1f", $total_queries / sizeof($sessions));
+  $s[t('Average time per query')] = sprintf("%.3f sec", $time['total'] / $total_queries / 1000);
+  $s[t('Average time per query: prepare')] = sprintf("%.3f sec", $time['prepare'] / $total_queries / 1000);
+  $s[t('Average time per query: process')] = sprintf("%.3f sec", $time['process'] / $total_queries / 1000);
+
+  // Chart for queries per timeslot
+  $chart = _apachesolr_stats_chart($data_per_granularity['queries'], $start_timeslot, $last_timeslot, $total_queries, $total_queries / ($last_timeslot-$start_timeslot+1));
+  $s[t('Total queries, by @granularity', array('@granularity' => $granularity['name']))] = $chart;
+
+  // Chart for average time per timeslot
+  $data = array();
+  foreach ($data_per_granularity['total_time'] as $timeslot => $value) {
+    $data[$timeslot] = $value / $count_per_granularity[$timeslot];
+  }
+  // Call with average_empty = FALSE
+  $chart = _apachesolr_stats_chart($data, $start_timeslot, $last_timeslot, $total_queries, $time['total'] / $total_queries);
+  $s[t('Average time per query, by @granularity (miliseconds)', array('@granularity' => $granularity['name']))] = $chart;
+
+  // Chart for users per timeslot
+  $chart = _apachesolr_stats_chart($data_per_granularity['users_per_slot'], $start_timeslot, $last_timeslot, $total_queries, sizeof($users) / ($last_timeslot-$start_timeslot+1));
+  $s[t('Total unique users executing queries, by @granularity', array('@granularity' => $granularity['name']))] = $chart;
+
+  // Chart for field usage
+  foreach ($field_usage as $fieldname => $count) {
+    $chd = "";
+  }
+  $chl = implode('|', array_keys($field_usage));
+  $chd = implode(',', $field_usage);
+  $height = 30+sizeof($field_usage)*35;
+  $chart = "<img src='http://chart.apis.google.com/chart?chxt=y&cht=bhs&chma=30,100,20,20&chd=t:{$chd}&chs=350x{$height}&chds=0,{$total_queries}&chxl=0:|{$chl}'>";
+  $s[t('Field usage', array('@granularity' => $granularity['name']))] = $chart;
+
+  // Create the output HTML.
+  $output = t('This is an overview of Apache Solr usage and performance.');
+  foreach ($s as $head => $value) {
+    // Table data
+    $rows[] = array(
+      "data" => array(
+        array('data' => $head, 'header' => true, 'style' => 'width:33%'),
+        array('data' => $value),
+      )
+    );
+  }
+  $output .= theme('table', array(), $rows);
+  return $output;
+}
+
+function _apachesolr_stats_chart($data, $start_timeslot, $last_timeslot, $total_queries, $average = FALSE) {
+  #$chart_prefix = "http://chart.apis.google.com/chart?cht=lc&chm=o,FF9900,0,-1,5.0&chs=350x100&chdlp=b&chma=10,10,10,10&chd=t:";
+  $chart_prefix = "http://chart.apis.google.com/chart?cht=lc&chs=350x100&chdlp=b&chma=30,100,20,20&chd=t:"; 
+  unset($chd);
+  $chd_min = 9999999;
+  $chd_max = 0;
+  $total = 0;
+  for ($t = $start_timeslot; $t<=$last_timeslot; $t++) {
+    $num = $data[$t]+0;
+    $chd_min = ($chd_min > $num) ? $num : $chd_min;
+    $chd_max = ($chd_max < $num) ? $num : $chd_max;
+    $chd[] = $num;
+  }
+  $chd = array_reverse($chd);
+  if ($count > 0) {
+    $chd_avg = $total / $count;
+  } else {
+    $chd_avg = $num;
+  }
+  $image_url = $chart_prefix . implode(",", $chd) . "&chds=$chd_min,$chd_max"; #&chdl=". t('Queries per minute');
+  // Add labels
+  $image_url .= "&chxl=0:|". intval($chd_min) ."|". intval($chd_max);
+  if ($average !== FALSE) {
+    $image_url .=sprintf("|1:|%s=%.2f", t('average'), $average);
+    $image_url .= "&chxp=1," . intval($average/$chd_max*100);
+    $chxt = "y,r";
+  } else {
+    $chxt = "y";
+  }
+  $image_url .= "&chxt=$chxt";
+  return "<img src='$image_url'>";
+}
+
+/**
+ * Implementation of hook_cron().
+ *
+ * Remove expired log messages.
+ */
+function apachesolr_stats_cron() {
+  db_query('DELETE FROM {apachesolr_stats} WHERE timestamp < %d', time() - variable_get('apachesolr_stats_flush_log_timer', 604800));
+}
+
+/**
+ * Implementation of apachesolr_search_result_ater().
+ */
+ /*
+function apachesolr_stats_apachesolr_search_result_alter($doc) {
+}
+*/