Github user gatorsmile commented on the issue:
https://github.com/apache/spark/pull/15690
Found another side effect caused by implicit casting. When we having `CAST`
in the filter conditions, we are unable to push down these filters into the
data sources. Performance could be very bad if users do not properly specify
the data types of these literals.
For example, when the data type of `a` is integer, the following filter can
be pushed down to the parquet:
```
spark.read.parquet(path).filter("a < 100")
```
However, users will not see the filter push down if the literal is not an
integer.
```
spark.read.parquet(path).filter("a < 100.0")
```
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