[CALCITE-4724] In JDBC adapter for ClickHouse, implement Values by generating SELECT without FROM

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.27.0
• Fix Version/s: 1.28.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Unassigned
• Reporter: Enze Liu
• Created: 11/Aug/21 05:48
• Updated: 14/May/22 01:00
• Resolved: 14/Aug/21 19:46

Description

In JDBC adapter for ClickHouse, implement Values by generating SELECT without FROM. In ClickHouseSqlDialect, the supportsAliasedValues() method should return false.

We use ClickHouseSqlDialect to do some sql optimize.  For sql select 1, in the process of sqlNode → relNode → sqlNode, the sql string will be transformed to 

SELECT *
FROM (VALUES (1)) AS `t` (`EXPR$0`)

Since clickhouse is not support AliasedValues, all we need to do is to extend ClickHouseSqlDialect and make `supportsAliasedValues` return false. 

Maybe this kind of behavior can integrated into core? 

If needed, the pull request is ready.

Issue Links

• is related to: CALCITE-3191 In JDBC adapter for MySQL, implement Values by generating SELECT without FROM
• links to: GitHub Pull Request #2480