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_r231356980
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File path: fe/src/main/java/org/apache/doris/planner/OlapScanNode.java
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@@ -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:
I think dividing `FeConstants.default_replication_num` is not a good way.
Because table's number of replica maybe not equal with it, and even they are
equal, when balancing or some BE is down, `tablet.getQueryableReplicas` won't
return replica which isn't available. And then, `computeStats` will get a wrong
`cardinality`.
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