Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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None
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None
Description
The estimateRowCount method of DataSetCalc didn't work now.
If I run the following code,
Table table = tableEnv .fromDataSet(data, "a, b, c") .where("a == 1") .groupBy("a") .select("a, a.avg, b.sum, c.count");
the cost of every node in Optimized node tree is :
DataSetAggregate(groupBy=[a], select=[a, AVG(a) AS TMP_0, SUM(b) AS TMP_1, COUNT(c) AS TMP_2]): rowcount = 1000.0, cumulative cost = {3000.0 rows, 5000.0 cpu, 28000.0 io}
DataSetCalc(select=[a, b, c], where=[=(a, 1)]): rowcount = 1000.0, cumulative cost = {2000.0 rows, 2000.0 cpu, 0.0 io}
DataSetScan(table=[[_DataSetTable_0]]): rowcount = 1000.0, cumulative cost = {1000.0 rows, 1000.0 cpu, 0.0 io}
We expect the input rowcount of DataSetAggregate less than 1000, however the actual input rowcount is still 1000 because the the estimateRowCount method of DataSetCalc didn't work.
There are two reasons caused to this:
1. Didn't provide custom metadataProvider yet. So when DataSetAggregate calls RelMetadataQuery.getRowCount(DataSetCalc) to estimate its input rowcount which would dispatch to RelMdRowCount.
2. DataSetCalc is subclass of SingleRel. So previous function call would match getRowCount(SingleRel rel, RelMetadataQuery mq) which would never use DataSetCalc.estimateRowCount.
The question would also appear to all Flink RelNodes which are subclass of SingleRel.
I plan to resolve this problem by adding a FlinkRelMdRowCount which contains specific getRowCount of Flink RelNodes.
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