[jira] [Closed] (CALCITE-4997) Keep APPROX_COUNT_DISTINCT in some SqlDialects

["Liya Fan (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-4997?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Liya Fan closed CALCITE-4997.
-----------------------------

Resolved in release 1.30.0 (2022-03-20)

> Keep APPROX_COUNT_DISTINCT in some SqlDialects
> ----------------------------------------------
>
>                 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: Jiajun Xie
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.30.0
>
>          Time Spent: 1h 50m
>  Remaining Estimate: 0h
>
> Summary:  Some engines(Hive,Spark,BigQuery,Oracle,Snowflake) support APPROX_COUNT_DISTINCT function, while others do not. So we can use the parameter *SqlDialect#supportsApproxCountDistinct* to control whether to use APPROX_COUNT_DISTINCT(It is the same as APPROX_DISTINCT for Presto).
> ----
> Problem: Before fix for all SqlDialects
> {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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