[GitHub] [incubator-doris] xinyiZzz commented on a change in pull request #8695: [enhancement] update broadcast join cost algorithm

[GitBox]

xinyiZzz commented on a change in pull request #8695:
URL: https://github.com/apache/incubator-doris/pull/8695#discussion_r836383494



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File path: 
fe/fe-core/src/main/java/org/apache/doris/planner/JoinCostEvaluation.java
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@@ -147,7 +149,7 @@ public long constructHashTableSpace() {
                 Math.pow(1.5, (int) ((Math.log((double) 
rhsTreeCardinality/4096) / Math.log(1.5)) + 1)) * 4096;
         double nodeOverheadSpace = nodeArrayLen * 16;
         double nodeTuplePointerSpace = nodeArrayLen * rhsTreeTupleIdNum * 8;
-        return Math.round((bucketPointerSpace + (double) rhsTreeCardinality * 
rhsTreeAvgRowSize
+        return Math.round((bucketPointerSpace + (double) rhsTreeCardinality * 
rhsTreeAvgRowSize * COMPRESSION_RATIO

Review comment:
       The `avgRowSize` statistics caused by the compression ratio are 
inaccurate,
   I understand that corrections should be made in `computeStats` of 
OlapScanNode, not in JoinCostEvaluation, until more accurate statistics 
collection is achieved.
   
   
![image](https://user-images.githubusercontent.com/13197424/160399501-24112608-51c8-45a1-9d64-417285ef029d.png)




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