34c85c962f
this change improves performance of tpch q20. on sf500, improved from 6.3sec to 1.1 sec this change has no impaction on tpcds when column stats is unknown, the basic algorithm to estimate left semi join output row count is its left child output row count. q1: "A left semi join B on A.x=B.x" the output row is estimated as A.rowCount. But the basic algorithm is not good to following pattern: q2: "A left semi join filter(B) on A.x=B.x" Because there is a filter on B, usually this left semi join also reduce the row count of A, and we estimate the output of q2 as A.rowCount * Filter.rowCount/B.rowCount
新加case注意事项
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变量名前要写 def，否则是全局变量，并行跑的 case 的时候可能被其他 case 影响。
Problematic code:
ret = ***Correct code:
def ret = *** -
尽量不要在 case 中 global 的设置 session variable，或者修改集群配置，可能会影响其他 case。
Problematic code:
sql """set global enable_pipeline_x_engine=true;"""Correct code:
sql """set enable_pipeline_x_engine=true;""" -
如果必须要设置 global，或者要改集群配置，可以指定 case 以 nonConcurrent 的方式运行。
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case 中涉及时间相关的，最好固定时间，不要用类似 now() 函数这种动态值，避免过一段时间后 case 就跑不过了。
Problematic code:
sql """select count(*) from table where created < now();"""Correct code:
sql """select count(*) from table where created < '2023-11-13';"""