[GitHub] [incubator-doris] imay opened a new issue #1520: Refactor storage aggregate_func.h

[GitBox <gi...@apache.org>]

imay opened a new issue #1520: Refactor storage aggregate_func.h
URL: https://github.com/apache/incubator-doris/issues/1520
 
 
   I want to refactor be/src/olap/aggregate_func.h. Current implementation have some problems.
   
   Now, Storage maintain two function map, one for aggregate function, the other for finalize function. I want to introduce a new struct AggregateInfo to enclose these two functions. And then user only need get one object to use aggregate functions.
   
   And what's more, I want to introduce a new function init, then for an aggregate operation, there are three functions: init, update, finalize. Which is the same with query engine. And for many aggregate operations, there is no finalize operation.
   
   For handling null, current implementation is bad. First we use a byte to represent null, which is a waste; secondly our memory format likes `null_byte|column_value|null_byte|column_value`, which makes column_value is not aligned, which I think a harm for performance. However, in this patch I don't want to handle it. I will leave it and fix it in another patch.
   
   @kangkaisen 
   
   related to #1486 

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