[CALCITE-4997] Keep APPROX_COUNT_DISTINCT in some SqlDialects

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Resolved
• Affects Version/s: 1.29.0
• Fix Version/s: 1.30.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Unassigned
• Reporter: Jiajun Xie
• Created: 02/Feb/22 07:14
• Updated: 19/Mar/22 09:16
• Resolved: 14/Feb/22 06:23

Description

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).

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Problem: Before fix for all SqlDialects

SELECT APPROX_COUNT_DISTINCT(product_id)
FROM foodmart.product

will be 

SELECT COUNT(DISTINCT product_id)
FROM foodmart.product

This can cause many tasks to run too slowly.

Issue Links

• links to: GitHub Pull Request #2710