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https://issues.apache.org/jira/browse/CALCITE-4809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17421248#comment-17421248
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Quan Chao commented on CALCITE-4809:
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i had pull requests #2550
> Mixed merge join result is incomplete
> --------------------------------------
>
> Key: CALCITE-4809
> URL: https://issues.apache.org/jira/browse/CALCITE-4809
> Project: Calcite
> Issue Type: Bug
> Components: linq4j
> Affects Versions: 1.26.0
> Reporter: Quan Chao
> Priority: Major
>
> The result of mixed merge join is incomplete. The merge join relies on the
> row data of the two tables to be sorted by the join field, but if the left
> table itself is a left join, nulls may appear due to mismatches, causing the
> entire join to end early。
> EG：
> t1 left join t2 on t1.id=t2.id join t3 on t2.id=t3.id;
> t1 rows: 1,2,3,4
> t2 rows: 1,2,4
> t3 rows: 1.2.3.4
> final result is:1,2. but 4 is lost;
> when MergeJoinEnumerator left (t1xt2) come to: 3,null, right (t3) is 3,
> the null <3 cause left advance finish wrong
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