Major Description
A benchmark test result is 10x slower when the generated function is too long :
ignore("max function length of wholestagecodegen") {
val N = 20 << 15
val benchmark = new Benchmark("max function length of wholestagecodegen", N)
def f(): Unit = sparkSession.range(N)
.selectExpr(
"id",
"(id & 1023) as k1",
"cast(id & 1023 as double) as k2",
"cast(id & 1023 as int) as k3",
"case when id > 100 and id <= 200 then 1 else 0 end as v1",
"case when id > 200 and id <= 300 then 1 else 0 end as v2",
"case when id > 300 and id <= 400 then 1 else 0 end as v3",
"case when id > 400 and id <= 500 then 1 else 0 end as v4",
"case when id > 500 and id <= 600 then 1 else 0 end as v5",
"case when id > 600 and id <= 700 then 1 else 0 end as v6",
"case when id > 700 and id <= 800 then 1 else 0 end as v7",
"case when id > 800 and id <= 900 then 1 else 0 end as v8",
"case when id > 900 and id <= 1000 then 1 else 0 end as v9",
"case when id > 1000 and id <= 1100 then 1 else 0 end as v10",
"case when id > 1100 and id <= 1200 then 1 else 0 end as v11",
"case when id > 1200 and id <= 1300 then 1 else 0 end as v12",
"case when id > 1300 and id <= 1400 then 1 else 0 end as v13",
"case when id > 1400 and id <= 1500 then 1 else 0 end as v14",
"case when id > 1500 and id <= 1600 then 1 else 0 end as v15",
"case when id > 1600 and id <= 1700 then 1 else 0 end as v16",
"case when id > 1700 and id <= 1800 then 1 else 0 end as v17",
"case when id > 1800 and id <= 1900 then 1 else 0 end as v18")
.groupBy("k1", "k2", "k3")
.sum()
.collect()
benchmark.addCase(s"codegen = F")
{ iter => sparkSession.conf.set("spark.sql.codegen.wholeStage", "false") f() }benchmark.addCase(s"codegen = T")
{ iter => sparkSession.conf.set("spark.sql.codegen.wholeStage", "true") sparkSession.conf.set("spark.sql.codegen.MaxFunctionLength", "10000") f() }benchmark.run()
/*
Java HotSpot(TM) 64-Bit Server VM 1.8.0_111-b14 on Windows 7 6.1
Intel64 Family 6 Model 58 Stepping 9, GenuineIntel
max function length of wholestagecodegen: Best/Avg Time(ms) Rate(M/s) Per Row(ns) Relative
------------------------------------------------------------------------------------------------
codegen = F 443 / 507 1.5 676.0 1.0X
codegen = T 3279 / 3283 0.2 5002.6 0.1X
*/
}
