MongoDB-aggregation-guide.pdf

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1、MongoDBAggregationandDataProcessingRelease2.4.6MongoDBDocumentationProjectSeptember11,2013Contents1AggregationIntroduction31.1AggregationModalities..........................................3AggregationPipelines...........................................3Map-Reduce..................................

2、..............3SinglePurposeAggregationOperations.................................61.2AdditionalFeaturesandBehaviors....................................62AggregationConcepts72.1AggregationPipeline...........................................7Pipeline..................................................

3、7PipelineExpressions...........................................9AggregationPipelineBehavior......................................92.2Map-Reduce................................................10Map-ReduceJavaScriptFunctions....................................11Map-ReduceBehavior....................

4、......................112.3SinglePurposeAggregationOperations.................................11Count...................................................11Distinct..................................................12Group...................................................132.4AggregationMechanics...

5、.......................................14AggregationPipelineOptimization....................................14AggregationPipelineLimits.......................................15AggregationPipelineandShardedCollections..............................15Map-ReduceandShardedCollections...................

6、...............16MapReduceConcurrency........................................173AggregationExamples173.1AggregationwiththeZipCodeDataSet.................................17DataModel................................................18ReturnStateswithPopulationsabove10Million...........................

7、.18ReturnAverageCityPopulationbyState.................................19ReturnLargestandSmallestCitiesbyState...............................193.2AggregationwithUserPreferenceData.................................2