hive之mapjoin

2021-12-11 11:02:01 作者：互联网

hive 的mapjoin起作用了我们如何确定？

只是inner join 的时候

看日志吧，最为直观：

2021-12-10 12:05:41	Starting to launch local task to process map join;	maximum memory = 954728448
2021-12-10 12:05:44	Processing rows:	200000	Hashtable size:	199999	Memory usage:	135058920	percentage:	0.141
2021-12-10 12:05:44	Dump the side-table into file: file:/tmp/hive_2021-12-10_11-47-34_913_2061727660300134431-1/-local-10007/HashTable-Stage-13/MapJoin-mapfile10--.hashtable
2021-12-10 12:05:44	Uploaded 1 File to: file:/tmp/hive_2021-12-10_11-47-34_913_2061727660300134431-1/-local-10007/HashTable-Stage-13/MapJoin-mapfile10--.hashtable (3517 bytes)
2021-12-10 12:05:44	Dump the side-table into file: file:/tmp/hive_2021-12-10_11-47-34_913_2061727660300134431-1/-local-10007/HashTable-Stage-13/MapJoin-mapfile12--.hashtable
2021-12-10 12:05:44	Uploaded 1 File to: file:/tmp/hive_2021-12-10_11-47-34_913_2061727660300134431-1/-local-10007/HashTable-Stage-13/MapJoin-mapfile12--.hashtable (8683158 bytes)
2021-12-10 12:05:44	End of local task; Time Taken: 3.034 sec.
Execution completed successfully

关键点：

Starting to launch local task to process map join; 这个说的够直白了吧
Uploaded 1 File to: file:/tmp/hive_2021-12-10_11-47-34_913_2061727660300134431-1/-local-10007/HashTable-Stage-13/MapJoin-mapfile10--.hashtable hashtable
end of local task
起一个local task 映射成一个hashtable

标签：10,12,05,hive,mapjoin,2021,file,local
来源： https://blog.csdn.net/weixin_36630761/article/details/121853242