# Operators In Execution Plan 
+ Operators in execution plans
  + Aggregate data class operators
    + `Hash Aggregate` 
    + `Stream Aggregate` 
  + Scan data class operators
  + Table join class operators

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We categorize the operators in the execution plan in three dimensions: aggregation, scanning, and connection.
In aggregate data class operators, we can divide it into two categories: Hash Aggregate and Stream Aggreate