hive的几个重点调优方法 1.Fetch抓取(Hive可以避免进行MapReduce) 2.MapJoin 3.使用分区剪裁、列剪裁 4.数据倾斜 Map数 小文件进行合并 reduce数 5.JVM重用 1.Fetch抓取(Hive可以避免进行MapReduce) Hive中对某些情况的查询可以不必使用MapReduce计算。例如:SELECT * FROM employees;在这种情况下,...猜...
比较运算符,以及in的type都是range。 EXPLAIN SELECT * FROM app_log AS temp WHERE id>100 LIMIT 199 1. ref:非唯一性索引访问 EXPLAIN SELECT * FROM app_log AS temp WHERE dt='2015-01-02' LIMIT 199 1. eq_ref:使用唯一性索引查找(主键或唯一索引) EXPLAIN SELECT * FROM app_log JOIN app_det...
Note: In the following descriptions, the symbol & means 'address of'. void main(): The main function must print your name, call readInts to 1. Explain what the JVM does when it encounters a synchronized directive. Hint: c...
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