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https://issues.apache.org/jira/browse/CALCITE-4997?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17486087#comment-17486087
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Julian Hyde commented on CALCITE-4997:
--------------------------------------
Can you explain why you think it was incorrect in this case? It is certainly
*valid* to transform approximate to exact (i.e. the results will not be
incorrect), and may be the best plan if there is no way to evaluate
approximately.
> approx_count_distinct function was incorrectly converted to count(distinct )
> ----------------------------------------------------------------------------
>
> Key: CALCITE-4997
> URL: https://issues.apache.org/jira/browse/CALCITE-4997
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.29.0
> Reporter: xiejiajun
> Priority: Major
>
> {code:java}
> SELECT APPROX_COUNT_DISTINCT(product_id)
> FROM foodmart.product
> {code}
> will be
> {code:java}
> SELECT COUNT(DISTINCT product_id)
> FROM foodmart.product
> {code}
> This can cause many tasks to run too slowly.
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