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` if all values are `Literal`, this
is a real case from production:
```sql
create table t1 using parquet as select * from range(100);
create table t2 using parquet as select * from range(200);
create temp view v1 as
select 'a' as event_type, * from t1
union all
select CASE WHEN id = 1 THEN 'b' WHEN id = 3 THEN 'c' end as event_type, *
from t2
explain select * from v1 where event_type = 'a';
```
Before this PR:
```
== Physical Plan ==
Union
:- *(1) Project [a AS event_type#30533, id#30535L]
: +- *(1) ColumnarToRow
: +- FileScan parquet default.t1[id#30535L] Batched: true, DataFilters:
[], Format: Parquet
+- *(2) Project [CASE WHEN (id#30536L = 1) THEN b WHEN (id#30536L = 3) THEN
c END AS event_type#30534, id#30536L]
+- *(2) Filter (CASE WHEN (id#30536L = 1) THEN b WHEN (id#30536L = 3)
THEN c END = a)
+- *(2) ColumnarToRow
+- FileScan parquet default.t2[id#30536L] Batched: true,
DataFilters: [(CASE WHEN (id#30536L = 1) THEN b WHEN (id#30536L = 3) THEN c END
= a)], Format: Parquet
```
After this PR:
```
== Physical Plan ==
*(1) Project [a AS event_type#8, id#4L]
+- *(1) ColumnarToRow
+- FileScan parquet default.t1[id#4L] Batched: true, DataFilters: [],
Format: Parquet
```
### 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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