[CALCITE-4809] Mixed merge join result is incomplete

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.26.0
• Component/s: linq4j
• Labels: pull-request-available
• Assignee: Unassigned
• Reporter: super486
• Created: 28/Sep/21 06:47
• Updated: 22/Dec/21 03:33

Description

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

Issue Links

• links to: GitHub Pull Request #2550
• links to: GitHub Pull Request #2574