[jira] [Resolved] (CALCITE-3221) Add MergeUnion operator in Enumerable convention

["Ruben Q L (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-3221?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ruben Q L resolved CALCITE-3221.
--------------------------------
    Resolution: Fixed

Done via https://github.com/apache/calcite/commit/4cd90f36c3cf9a012e34f14129a907a4ce99c6f5

Thanks everyone for the feedback, especially [~vladimirsitnikov] for his suggestions to improve the patch.

> Add MergeUnion operator in Enumerable convention
> ------------------------------------------------
>
>                 Key: CALCITE-3221
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3221
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.19.0
>            Reporter: Stamatis Zampetakis
>            Assignee: Ruben Q L
>            Priority: Minor
>              Labels: pull-request-available
>             Fix For: 1.27.0
>
>         Attachments: screenshot-1.png
>
>          Time Spent: 15h 10m
>  Remaining Estimate: 0h
>
> Currently, the union operation offered by Calcite (see [EnumerableDefaults.union|https://github.com/apache/calcite/blob/d98856bf1a5f5c151d004b769e14bdd368a67234/linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java#L2747]) "breaks" the collation (if any) of its inputs.
> The goal of this issue is to create a new union algorithm in Enumerable convention (EnumerableMergeUnion) that, given the fact that its inputs are sorted by the same collation, will return the union / union all result respecting this collation.
> Most likely the implementation of the merge join can be useful.



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