[GitHub] imay commented on a change in pull request #256: Improve cardinality, avgRowSize, numNodes stat info in OlapScanNode

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

imay commented on a change in pull request #256: Improve cardinality, avgRowSize, numNodes stat info in OlapScanNode
URL: https://github.com/apache/incubator-doris/pull/256#discussion_r231081814
 
 

 ##########
 File path: fe/src/main/java/org/apache/doris/planner/OlapScanNode.java
 ##########
 @@ -447,6 +465,13 @@ private void addScanRangeLocations(Partition partition,
                 scanRangeLocations.addToLocations(scanRangeLocation);
                 paloRange.addToHosts(new TNetworkAddress(ip, port));
                 tabletIsNull = false;
+
+                //for CBO
+                if (replica.getRowCount() != -1) {
+                    cardinality += replica.getRowCount();
+                    totalBytes += replica.getDataSize();
+                }
+                scanBackendIds.add(backend.getId());
 
 Review comment:
   OlapScanNode will put one tablet's all replicas to paloRange, because Coordinator will balance these replicas and try to make that each backend will scan same rows.
   
   However, not all replicas will be read. If table has 3 replica, only one can be read. And this patch will add scan rows three times.
   
   So, you can change cardinality and totalBytes outsize for each tablet other than replica.

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