[GitHub] [spark] Bahigac commented on pull request #35220: [SPARK-37922][SQL] Combine to one cast if we can safely up-cast two casts

[GitBox <gi...@apache.org>]

Bahigac commented on PR #35220:
URL: https://github.com/apache/spark/pull/35220#issuecomment-1242201044

   > ### What changes were proposed in this pull request?
   > 
   > 
   > 
   > This PR improves `SimplifyCasts` to combine into one cast if they are both `NumericType` and can safely up-cast two casts. For example:
   > 
   > 
   > 
   > ```scala
   > 
   > spark.sql("CREATE TABLE t1 (id int) using parquet")
   > 
   > spark.sql("SELECT CAST(CAST(id AS DECIMAL(10, 0)) AS DECIMAL(12, 2)) FROM t1").explain(true)
   > 
   > ```
   > 
   > Before this pr:
   > 
   > ```
   > 
   > == Optimized Logical Plan ==
   > 
   > Project [cast(cast(id#1 as decimal(10,0)) as decimal(12,2)) AS casted#0]
   > 
   > +- Relation default.t1[id#1] parquet
   > 
   > ```
   > 
   > 
   > 
   > After this pr:
   > 
   > ```
   > 
   > == Optimized Logical Plan ==
   > 
   > Project [cast(id#1 as decimal(12,2)) AS casted#0]
   > 
   > +- Relation default.t1[id#1] 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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