manuzhang opened a new pull request, #36615:
URL: https://github.com/apache/spark/pull/36615
### What changes were proposed in this pull request?
When analyzing, apply WidenSetOperationTypes after other rules.
### Why are the changes needed?
The following SQL returns 1.00 while 1.00000000000000000000 is expected
since union should pick the wider precision, the `Decimal(38,20)` from `v / v` .
```
CREATE OR REPLACE TEMPORARY VIEW t3 AS VALUES (decimal(1)) tbl(v);
CREATE OR REPLACE TEMPORARY VIEW t4 AS SELECT CAST(v AS DECIMAL(18, 2)) AS v
FROM t3;
SELECT CAST(1 AS DECIMAL(28, 2))
UNION ALL
SELECT v / v FROM t4;
```
Checking the analyzed logical plan of the above SQL, `Project [cast((v /
v)#236 as decimal(28,2)) AS (v / v)#237]` is added by `WidenSetOperationTypes`
before `DecimalPrecision` promoting precision for the divide. The result of `v
/ v` is cast to the narrower `decimal(28,2)`.
```
== Analyzed Logical Plan ==
CAST(1 AS DECIMAL(28,2)): decimal(28,2)
Union false, false
:- Project [CAST(1 AS DECIMAL(28,2))#235]
: +- Project [cast(1 as decimal(28,2)) AS CAST(1 AS DECIMAL(28,2))#235]
: +- OneRowRelation
+- Project [cast((v / v)#236 as decimal(28,2)) AS (v / v)#237]
+- Project [CheckOverflow((promote_precision(cast(v#228 as
decimal(18,2))) / promote_precision(cast(v#228 as decimal(18,2)))),
DecimalType(38,20), false) AS (v / v)#236]
+- SubqueryAlias t4
+- Project [cast(v#226 as decimal(18,2)) AS v#228]
+- SubqueryAlias t3
+- SubqueryAlias tbl
+- LocalRelation [v#226]
```
Hence, I propose to apply `WidenSetOperationTypes` after `DecimalPrecision`.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Add UT.
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