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Posted to commits@doris.apache.org by "xzj7019 (via GitHub)" <gi...@apache.org> on 2023/06/12 08:21:54 UTC
[GitHub] [doris] xzj7019 commented on a diff in pull request #20642: [tpcds](nereids) estimate distribution cost by byte size instead of row count
xzj7019 commented on code in PR #20642:
URL: https://github.com/apache/doris/pull/20642#discussion_r1226268711
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/cost/CostModelV1.java:
##########
@@ -191,7 +191,7 @@ public Cost visitPhysicalDistribute(
return CostV1.of(
0,
0,
- childStatistics.getRowCount() * Math.pow(beNumber, 0.5));
Review Comment:
In cost model v1, we use row count as the unified metrics to measure the cost. So here we would better to also use row-count based cost system, if we need to distinguish the distribute cost for different cases, we can use a factor parameter using dataSize as the input with a minimal value 1.
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/cost/CostModelV1.java:
##########
@@ -161,27 +161,27 @@ public Cost visitPhysicalPartitionTopN(PhysicalPartitionTopN<? extends Plan> par
@Override
public Cost visitPhysicalDistribute(
PhysicalDistribute<? extends Plan> distribute, PlanContext context) {
+ int kBytes = 1024;
Statistics childStatistics = context.getChildStatistics(0);
DistributionSpec spec = distribute.getDistributionSpec();
+ int beNumber = ConnectContext.get().getEnv().getClusterInfo().getBackendsNumber(true);
+ beNumber = Math.max(1, beNumber);
+ double dataSize = childStatistics.computeSize() / kBytes; // in K bytes
// shuffle
if (spec instanceof DistributionSpecHash) {
return CostV1.of(
0,
0,
- childStatistics.getRowCount());
Review Comment:
In cost model v1, we use row count as the unified metrics to measure the cost. So here we would better to also use row-count based cost system, if we need to distinguish the distribute cost for different cases, we can use a factor parameter using dataSize as the input with a minimal value 1.
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