- 如果reduce個數過少(配置文件設置,而非自動生成),可能會出現錯誤:013-01-16 18:04:49,311 FATAL org.apache.hadoop.mapred.Child: Error running child : java.lang.OutOfMemoryError: allocLargeObjectOrArray
- hive能自動識別join是否可以轉化位mapjion。如果非要手工指定的話,可能會出現錯誤:
2013-01-16 03:38:48 Starting to launch local task to process map join; maximum memory = 1048576000
2013-01-16 03:38:51 Processing rows: 200000 Hashtable size: 199999 Memory usage: 90039472 rate: 0.086
...............................
2013-01-16 03:39:07 Processing rows: 2300000 Hashtable size: 2299999 Memory usage: 961646184 rate: 0.917
- 如果設置hive空值默認爲'-1',那麼在select one 時選出的會將'-1'顯示爲null。select * 會顯示‘-1’
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空值顯示爲NULL,而非'NULL'
CASE sms_send_count WHEN NULL THEN -1 ELSE 0 END,CASE sms_bill_count WHEN NULL THEN -1 ELSE 0 END,CASE sms_people_count WHEN NULL THEN -1 ELSE 0 END,
FAILED: Error in semantic analysis: Line 4:25 Argument type mismatch ''NULL'': The expressions after WHEN should have the same type with that after CASE: "bigint" is expected but "string" is found