Jiayi Liao created SPARK-26182:
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Summary: Cost increases when optimizing scalaUDF
Key: SPARK-26182
URL: https://issues.apache.org/jira/browse/SPARK-26182
Project: Spark
Issue Type: Bug
Components: Optimizer
Affects Versions: 2.4.0
Reporter: Jiayi Liao
Let's Assume that we have a udf called splitUDF which outputs a map data.
The SQL
{code:java}
select
g['a'], g['b']
from
( select splitUDF(x) as g from table) tbl
{code}
will be optimized to the same logical plan of
{code:java}
select splitUDF(x)['a'], splitUDF(x)['b'] from table
{code}
which means that the splitUDF is executed twice instead of once.
The optimization is from CollapseProject.
I'm not sure whether this is a bug or not. Please tell me if I was wrong about
this.
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