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https://issues.apache.org/jira/browse/CALCITE-4997?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17486860#comment-17486860
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xiejiajun commented on CALCITE-4997:
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I looked up some information and opened it in the dialect with this function:
- Hive:https://hivemall.incubator.apache.org/userguide/misc/approx.html
-
Spark:https://spark.apache.org/docs/3.1.2/sql-ref-functions-builtin.html#aggregate-functions
-
BigQuery:https://cloud.google.com/bigquery/docs/reference/standard-sql/approximate_aggregate_functions
- Oralce:https://docs.oracle.com/database/121/SQLRF/functions013.htm#SQLRF56900
-
Snowlake:https://docs.snowflake.com/en/sql-reference/functions/approx_count_distinct.html
-
Presto:https://prestodb.io/docs/current/functions/aggregate.html?highlight=approx_distinct#approximate-aggregate-functions
For presto, it‘s function name is slightly different.
For snowflake, it is not in SqlDialectFactoryimpl#simple (there are 34
instances of DatabaseProduct, so I think it may have been omitted before)
> 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
> Labels: pull-request-available
> Time Spent: 20m
> Remaining Estimate: 0h
>
> {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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