kasakrisz commented on code in PR #3430:
URL: https://github.com/apache/hive/pull/3430#discussion_r924515510
##########
ql/src/test/results/clientpositive/llap/check_constraint.q.out:
##########
@@ -2519,23 +2519,23 @@ STAGE PLANS:
Map 7
Map Operator Tree:
TableScan
- alias: t
+ alias: tmerge
Review Comment:
In the past the statement
```
explain MERGE INTO tmerge as t using nonacid as s ON t.key = s.key
WHEN MATCHED AND s.key < 5 THEN DELETE
WHEN MATCHED AND s.key < 3 THEN UPDATE set a1 = '1'
WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.a1, s.value)
```
was rewritten to
```
FROM
`tmerge` `t`
RIGHT OUTER JOIN
`default`.`nonacid` `s`
ON `t`.`key` = `s`.`key`
<insert branches>
```
In this patch I introduced a subquery because some of the target table
columns needed twice in case of iceberg target and it is generated in the same
way in case of updates.
```
FROM
(SELECT ROW__ID, `key`, `a1`, `value` FROM `default`.`tmerge`) `t`
RIGHT OUTER JOIN
`default`.`nonacid` `s`
ON `t`.`key` = `s`.`key`
<insert branches>
```
In both the new and the old plan TS you highlighted scans the same table:
tmerge
But in the old plane `tmerge` and `t` refers to the same object. In the new
plan the table does not have an alias so it is referenced by its name. The
alias `t` refers the subquery.
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