Notas agregadas de Mongo

Mongo es difícil de usar, principalmente porque no está acostumbrado a escribir muchas palabras

La documentación está muy bien escrita.

https://docs.mongodb.com/manual/reference/aggregation-variables/#agg-system-variables

 

 

https://docs.mongodb.com/manual/reference/operator/aggregation/sort/index.html

 

 

 

 

https://docs.mongodb.com/manual/reference/operator/aggregation/group/index.html

 

 

 

 

Este articulo esta bien.

https://www.jianshu.com/p/206f036bdfc5

 

Correspondiente a mongtemplate en springboot, está escrito así

 

 

 

Esto está muy bien escrito

https://kb.objectrocket.com/mongo-db/mongodb-group-by-multiple-fields-using-aggregation-function-464

 

db.sales.aggregate ( 
   [ 
     {$ sort: {item: -1, date: -1 }}, 
     { 
       $ group: 
         { 
           _id: "$ item" , 
           firstSalesDate: {$ first: "$ date" }, 
           firstId: {$ first: "$ _id" }, 
           firstRoot: {$ first: "$$ ROOT" }, 
         } 
     } 
   ] 
)

　　

Criterio criterio = Criterio.where ("xxx"). Is ("xxxx"). Y ("xxx"). Is (xxx);        
Aggregation aggregation = Aggregation.newAggregation ( 
                Aggregation.match (criterios), 
                Aggregation.sort (Sort.Direction.ASC, "createTime" ), 
                Aggregation.group ( "xx", "xx" ) 
                        .first ( "$ id"). as ("xx" ) 
                        .first ( "$ xxx"). as ("xx" ) 
                        .first ( "$ xxx"). as ("" xx " ) 
                        .first ( " $ xxxx "). as ("
                        .first ( "$ xxxx"). as ("xx" ) 
        );

La mayor dificultad es que $ _id se llama $ id en mongotemplate, less _ y Aggregation.ROOT, Aggregation.CURRENT