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https://issues.apache.org/jira/browse/FLINK-4604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15554768#comment-15554768
]
Anton Mushin commented on FLINK-4604:
-------------------------------------
I changed method
{{org.apache.flink.api.table.plan.nodes.dataset.DataSetAggregate#computeSelfCost}}
it is impermanent implementation for examle
{code}
override def computeSelfCost (planner: RelOptPlanner, metadata:
RelMetadataQuery): RelOptCost = {
val child = this.getInput
val rowCnt = metadata.getRowCount(child)
val rowSize = this.estimateRowSize(child.getRowType)
val aggCnt = this.namedAggregates.size
var resultCost = planner.getCostFactory.makeCost(rowCnt, rowCnt * aggCnt,
rowCnt * rowSize)
this.namedAggregates.foreach(x=>{
x.getKey.getAggregation.getKind match {
case SqlKind.STDDEV_POP =>
resultCost = resultCost.plus(planner.getCostFactory.makeCost(rowCnt,
rowCnt * aggCnt, rowCnt * rowSize))
case SqlKind.STDDEV_SAMP =>
resultCost = resultCost.plus(planner.getCostFactory.makeCost(rowCnt,
rowCnt * aggCnt, rowCnt * rowSize))
case SqlKind.VAR_SAMP =>
resultCost = resultCost.plus(planner.getCostFactory.makeCost(rowCnt,
rowCnt * aggCnt, rowCnt * rowSize))
case SqlKind.VAR_POP =>
resultCost = resultCost.plus(planner.getCostFactory.makeCost(rowCnt,
rowCnt * aggCnt, rowCnt * rowSize))
case default => None
}
})
resultCost
}
{code}
and i got next plan:
{noformat}
DataSetCalc(select=[CAST(POWER(/(-($f0, /(*($f1, $f1), $f2)), $f2), 0.5)) AS
$f0, CAST(POWER(/(-($f3, /(*($f1, $f1), $f2)), CASE(=($f2, 1), null, -($f2,
1))), 0.5)) AS $f1, CAST(/(-($f4, /(*($f1, $f1), $f2)), CASE(=($f2, 1), null,
-($f2, 1)))) AS $f2, CAST(/(-($f5, /(*($f1, $f1), $f2)), $f2)) AS $f3])
DataSetAggregate(select=[SUM($f6) AS $f0, SUM(_1) AS $f1, COUNT(_1) AS $f2,
SUM($f7) AS $f3, SUM($f8) AS $f4, SUM($f9) AS $f5])
DataSetCalc(select=[_1, _2, _3, _4, _5, _6])
DataSetScan(table=[[_DataSetTable_0]])
LogicalAggregate(group=[{}], EXPR$0=[STDDEV_POP($0)], EXPR$1=[STDDEV_SAMP($0)],
EXPR$2=[VAR_SAMP($0)], EXPR$3=[VAR_POP($0)])
LogicalProject(_1=[$0])
LogicalTableScan(table=[[_DataSetTable_0]])
{noformat}
> Add support for standard deviation/variance
> -------------------------------------------
>
> Key: FLINK-4604
> URL: https://issues.apache.org/jira/browse/FLINK-4604
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Timo Walther
> Assignee: Anton Mushin
> Attachments: 1.jpg
>
>
> Calcite's {{AggregateReduceFunctionsRule}} can convert SQL {{AVG, STDDEV_POP,
> STDDEV_SAMP, VAR_POP, VAR_SAMP}} to sum/count functions. We should add, test
> and document this rule.
> If we also want to add this aggregates to Table API is up for discussion.
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