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https://issues.apache.org/jira/browse/FLINK-6516?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16087085#comment-16087085
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ASF GitHub Bot commented on FLINK-6516:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3860#discussion_r127418874
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/PhysicalTableSourceScan.scala
---
@@ -70,4 +73,18 @@ abstract class PhysicalTableSourceScan(
def copy(traitSet: RelTraitSet, tableSource: TableSource[_]):
PhysicalTableSourceScan
+ override def estimateRowCount(mq: RelMetadataQuery): Double = {
+ val tableSourceTable = getTable.unwrap(classOf[TableSourceTable[_]])
+
+ if (tableSourceTable.getStatistic != FlinkStatistic.UNKNOWN) {
--- End diff --
Right, but in the current implementation the statistics of the
`TableSourceTable` are preferred over the stats of the `TableSource` (`if
(tableSourceTable.getStatistic != FlinkStatistic.UNKNOWN) { return rowcount;
}`).
If I see this correctly, the stats of the `TableSourceTable` are the stats
in the catalog, but a `FilterableTableSource` knows if a filter has been pushed
down and should have more accurate stats because it can apply the selectivity
of the pushed down filter.
So in my opinion the `TableSource` statistics should be preferred over the
static `TableSourceTable` stats.
Is my reasoning correct or did I overlook something @godfreyhe?
Thanks, Fabian
> using real row count instead of dummy row count when optimizing plan
> --------------------------------------------------------------------
>
> Key: FLINK-6516
> URL: https://issues.apache.org/jira/browse/FLINK-6516
> Project: Flink
> Issue Type: Improvement
> Components: Table API & SQL
> Reporter: godfrey he
> Assignee: godfrey he
>
> Currently, the statistic of {{TableSourceTable}} is {{UNKNOWN}} mostly, and
> the statistic from {{ExternalCatalog}} maybe is null also. Actually, only
> each {{TableSource}} knows its statistic exactly, especial for
> {{FilterableTableSource}} and {{PartitionableTableSource}}. So we can add
> {{getTableStats}} method in {{TableSource}}, and use it in TableSourceScan's
> estimateRowCount method to get real row count.
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