wangyum opened a new pull request #30222:
URL: https://github.com/apache/spark/pull/30222
### What changes were proposed in this pull request?
This pr simplify `CaseWhen` with `EqualTo`, for exmaple:
```sql
create table t(a int, b int, c int) using parquet;
SELECT *
FROM (SELECT CASE
WHEN a = 100 THEN 1
WHEN b > 1000 THEN 2
WHEN c IS NOT NULL THEN 3
END AS x
FROM t) tmp
WHERE x = 2
```
Before this PR:
```scala
== Physical Plan ==
*(1) Project [CASE WHEN (a#1 = 100) THEN 1 WHEN (b#2 > 1000) THEN 2 WHEN
isnotnull(c#3) THEN 3 END AS x#5]
+- *(1) Filter (CASE WHEN (a#1 = 100) THEN 1 WHEN (b#2 > 1000) THEN 2 WHEN
isnotnull(c#3) THEN 3 END = 2)
+- *(1) ColumnarToRow
+- FileScan parquet default.t[a#1,b#2,c#3] Batched: true, DataFilters:
[(CASE WHEN (a#1 = 100) THEN 1 WHEN (b#2 > 1000) THEN 2 WHEN isnotnull(c#3)
THEN 3 END = 2)], Format: Parquet, PartitionFilters: [], PushedFilters: [],
ReadSchema: struct<a:int,b:int,c:int>
```
After this PR:
```scala
== Physical Plan ==
*(1) Project [CASE WHEN (a#1 = 100) THEN 1 WHEN (b#2 > 1000) THEN 2 WHEN
isnotnull(c#3) THEN 3 END AS x#0]
+- *(1) Filter (b#2 > 1000)
+- *(1) ColumnarToRow
+- FileScan parquet default.t[a#1,b#2,c#3] Batched: true, DataFilters:
[(b#2 > 1000)], Format: Parquet, PartitionFilters: [], PushedFilters:
[GreaterThan(b,1000)], ReadSchema: struct<a:int,b:int,c:int>
```
### Why are the changes needed?
Improve query performance.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Unit test.
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