text: 'use strict';
  
  /**
   * explain_update.js
   *
   * Runs explain() and update() on a collection.
   */
  load('jstests/concurrency/fsm_libs/extend_workload.js');           // for extendWorkload
  load('jstests/concurrency/fsm_workloads/explain.js');              // for $config
  load('jstests/concurrency/fsm_workload_helpers/server_types.js');  // for isMongos
  
  var $config = extendWorkload($config, function($config, $super) {
  
      $config.states = Object.extend({
          explainBasicUpdate: function explainBasicUpdate(db, collName) {
              var res =
                  db[collName].explain('executionStats').update({i: this.nInserted}, {$set: {j: 49}});
              assertAlways.commandWorked(res);
              assertWhenOwnColl(function() {
                  assertWhenOwnColl.eq(1, explain.executionStats.totalDocsExamined);
  
                  // document should not have been updated.
                  var doc = db[collName].findOne({i: this.nInserted});
                  assertWhenOwnColl.eq(2 * this.nInserted, doc.j);
              }.bind(this));
          },
          explainUpdateUpsert: function explainUpdateUpsert(db, collName) {
              var res = db[collName]
                            .explain('executionStats')
                            .update({i: 2 * this.nInserted + 1},
                                    {$set: {j: 81}},
                                    /* upsert */ true);
              assertAlways.commandWorked(res);
              var stage = res.executionStats.executionStages;
  
              // if explaining a write command through mongos
              if (isMongos(db)) {
                  stage = stage.shards[0].executionStages;
              }
              assertAlways.eq(stage.stage, 'UPDATE');
              assertWhenOwnColl(stage.wouldInsert);
  
              // make sure that the insert didn't actually happen.
              assertWhenOwnColl.eq(this.nInserted, db[collName].find().itcount());
          },
          explainUpdateMulti: function explainUpdateMulti(db, collName) {
              var res = db[collName]
                            .explain('executionStats')
                            .update({i: {$lte: 2}},
                                    {$set: {b: 3}},
                                    /* upsert */ false,
                                    /* multi */ true);
              assertAlways.commandWorked(res);
              var stage = res.executionStats.executionStages;
  
              // if explaining a write command through mongos
              if (isMongos(db)) {
                  stage = stage.shards[0].executionStages;
              }
              assertAlways.eq(stage.stage, 'UPDATE');
              assertWhenOwnColl(!stage.wouldInsert);
              assertWhenOwnColl.eq(3, stage.nMatched);
              assertWhenOwnColl.eq(3, stage.nWouldModify);
          }
      },
                                     $super.states);
  
      $config.transitions = Object.extend(
          {explain: $config.data.assignEqualProbsToTransitions($config.states)}, $super.transitions);
  
      return $config;
  });
  