[SERVER] Streaming with ID on time

In some cases for timeseries (example below) optimizer may replace $group with $_internalStreamingGroup stage. In addition to all $group fields, it will also contain $monotonicIdFields field that lists all _id fields that are considered monotonic by the optimizer. If _id is a single expression, it will just contain a single element “_id”. Example of explain output with the new stage {         "explainVersion" : "1",         "stages" : [                 {                         "$cursor" : {                                 "queryPlanner" : {                                         "namespace" : "timeseries.system.buckets.Collection0",                                         "indexFilterSet" : false,                                         "parsedQuery" : {                                         },                                         "queryHash" : "17830885",                                         "planCacheKey" : "17830885",                                         "maxIndexedOrSolutionsReached" : false,                                         "maxIndexedAndSolutionsReached" : false,                                         "maxScansToExplodeReached" : false,                                         "winningPlan" : {                                                 "stage" : "COLLSCAN",                                                 "direction" : "forward"                                         },                                         "rejectedPlans" : [ ]                                 }                         }                 },                 {                         "$_internalUnpackBucket" : {                                 "include" : [                                         "price",                                         "time",                                         "symbol"                                 ],                                 "timeField" : "time",                                 "metaField" : "symbol",                                 "bucketMaxSpanSeconds" : 3600,                                 "assumeNoMixedSchemaData" : true,                                 "includeMinTimeAsMetadata" : true                 "internalQueryFacetBufferSizeBytes" : 104857600,                 "internalQueryFacetMaxOutputDocSizeBytes" : 104857600,                 "internalLookupStageIntermediateDocumentMaxSizeBytes" : 104857600,                 "internalDocumentSourceGroupMaxMemoryBytes" : 104857600,                 "internalQueryMaxBlockingSortMemoryUsageBytes" : 104857600,                 "internalQueryProhibitBlockingMergeOnMongoS" : 0,                 "internalQueryMaxAddToSetBytes" : 104857600,                 "internalDocumentSourceSetWindowFieldsMaxMemoryBytes" : 104857600,                 "internalQueryFrameworkControl" : "tryBonsai"         },         "command" : {                 "aggregate" : "system.buckets.Collection0",                 "pipeline" : [                         {                                 "$_internalUnpackBucket" : {                                         "timeField" : "time",                                         "metaField" : "symbol",                                         "bucketMaxSpanSeconds" : 3600,                                         "assumeNoMixedSchemaData" : true,                                 "includeMinTimeAsMetadata" : true [75/5353]                         }                 },                 {                         "$_internalBoundedSort" : {                                 "sortKey" : {                                         "time" : 1                                 },                                 "bound" : {                                         "base" : "min",                                         "offsetSeconds" : NumberLong(0)                                 },                                 "limit" : NumberLong(0)                         }                 },                 {                         "$_internalStreamingGroup" : {                                 "_id" : {                                         "symbol" : "$symbol",                                         "time" : {                                                 "$dateTrunc" : {                                                         "date" : "$time",                                                         "unit" : {                                                                 "$const" : "minute"                                                         },                                                         "binSize" : {                                                                 "$const" : 61                                                         }                                                 }                                         }                                 },                                 "high" : {                                         "$max" : "$price"                                 },                                 "low" : {                                         "$min" : "$price"                                 },                                 "open" : {                                         "$first" : "$price"                                 },                                 "close" : {                                         "$last" : "$price"                                 },                                 "$monotonicIdFields" : [                                         "time"                                 ]                         }                 }         ],         "serverInfo" : {                 "host" : "ip-10-122-10-70",                 "port" : 27017,                 "version" : "6.3.0-alpha-261-geac3840",                 "gitVersion" : "eac384080001c4ba2dbbb72cb79550deb215a79a"         },         "serverParameters" : {                 "internalQueryFacetBufferSizeBytes" : 104857600,                 "internalQueryFacetMaxOutputDocSizeBytes" : 104857600,                 "internalLookupStageIntermediateDocumentMaxSizeBytes" : 104857600,                 "internalDocumentSourceGroupMaxMemoryBytes" : 104857600,                 "internalQueryMaxBlockingSortMemoryUsageBytes" : 104857600,                 "internalQueryProhibitBlockingMergeOnMongoS" : 0,                 "internalQueryMaxAddToSetBytes" : 104857600,                 "internalDocumentSourceSetWindowFieldsMaxMemoryBytes" : 104857600,                 "internalQueryFrameworkControl" : "tryBonsai"         },         "command" : {                 "aggregate" : "system.buckets.Collection0",                 "pipeline" : [                         {                                 "$_internalUnpackBucket" : {                                         "timeField" : "time",                                         "metaField" : "symbol",                                         "bucketMaxSpanSeconds" : 3600,                                         "assumeNoMixedSchemaData" : true,                                         "usesExtendedRange" : false                                 }                         },                         {                                 "$sort" : {                                         "time" : 1                                 }                         },                         {                                 "$group" : {                                         "_id" : {                                                 "symbol" : "$symbol",                                                 "time" : {                                                         "$dateTrunc" : {                                                                 "date" : "$time",                                                                 "unit" : "minute",                                                                 "binSize" : 61                                                         }                                                 }                                         },                                         "high" : {                                                 "$max" : "$price"                                         },                                         "low" : {                                                 "$min" : "$price"                                         },                                         "open" : {                                                 "$first" : "$price"                                         },                                         "close" : {                                                 "$last" : "$price"                                         }                                 }                         }                 ],                 "cursor" : {                 },                 "collation" : {                         "locale" : "simple"                 }         },         "ok" : 1 }