ulysses-you commented on pull request #26875:
URL: https://github.com/apache/spark/pull/26875#issuecomment-646699595
Env: centos 7, 40cores, 4GB
---- test 1 ----
```
val df1 = spark.range(0, 20000, 1, 200).selectExpr("uuid() as c1")
val df2 = spark.range(0, 20000, 1, 200).selectExpr("uuid() as c2")
val start = System.currentTimeMillis
df1.join(df2).where("c2 like c1").count()
// 3 times test
// before 159228, 157541, 157721
// after 14378, 11545, 11498
println(System.currentTimeMillis - start)
```
---- test2 ----
```
// 17+1 length stirngs
val df1 = spark.range(0, 20000, 1,
200).selectExpr("concat('aaaaaaaaaaaaaaaaa', id%2) as c1")
val df2 = spark.range(0, 20000, 1,
200).selectExpr("concat('bbbbbbbbbbbbbbbbb', id%2) as c2")
val start = System.currentTimeMillis
df1.join(df2).where("c2 like c1").count()
// 3 times test
// before 90054, 90350, 90283
// after 13077, 10097, 9770
println(System.currentTimeMillis - start)
```
About 10x time performance improvement. Seems equals is more quickly than
compile pattern. And longer strings would make performance improvement better.
cc @HyukjinKwon
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