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https://issues.apache.org/jira/browse/CALCITE-4209?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde resolved CALCITE-4209.
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Fix Version/s: 1.26.0
Resolution: Fixed
Fixed in
[02904822|https://github.com/apache/calcite/commit/02904822bf987206c660e2afcdcb6e299d307094].
> In RelBuilder, add an option to not simplify LIMIT 0 to an empty relation
> -------------------------------------------------------------------------
>
> Key: CALCITE-4209
> URL: https://issues.apache.org/jira/browse/CALCITE-4209
> Project: Calcite
> Issue Type: Improvement
> Reporter: Steven Talbot
> Assignee: Julian Hyde
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.26.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> When you call {{relBuilder.limit(0, 0)}} it triggers a call to
> {{RelBuilder.empty}}
> [here|https://github.com/apache/calcite/blob/88d18185e6177c9df587bdd23dd4049f59adc2e4/core/src/main/java/org/apache/calcite/tools/RelBuilder.java#L2531].
> This is fine as the default behavior, but for cases where we intend to
> convert the relational algebra to SQL and display it somewhere, it would be
> preferable to turn this behavior off, either as an extra flag to this method
> or a configuration parameter. The call to {{empty()}} often results in a
> VALUES or a select list of literal NULLs, which looks ugly and can confuse a
> user.
> Moreover, there are certain databases (like BigQuery) that can cheaply handle
> a LIMIT 0 query as a form of validation, and if we munge the query with
> '{{empty()}}' we lose the ability to validate its correctness by going to the
> DB.
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