[
https://issues.apache.org/jira/browse/CALCITE-939?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14975558#comment-14975558
]
Julian Hyde commented on CALCITE-939:
-------------------------------------
I think it would really help future users/maintainers if you explain the
rationale. Basically, you want `matchNullFetch = true` if you are using an
implementation of Union that preserves order. If Union does not preserve order,
the limit is doing no useful work. If the Union does preserves order (and
merges on the sort key), you are still doing useful work if fetch is null,
because at least you have done the sort.
I can see the concept of "sort-preserving union" being useful in some other
rules, so I don't want it buried in an obscure flag.
> Add a flag to SortUnionTransposeRule to indicate if the rule should be
> applied when Sort.fetch is null.
> -------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-939
> URL: https://issues.apache.org/jira/browse/CALCITE-939
> Project: Calcite
> Issue Type: Improvement
> Reporter: Maryann Xue
> Assignee: Maryann Xue
> Priority: Minor
> Fix For: 1.5.0
>
> Attachments: CALCITE-939.patch
>
>
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
