原表src:
hive> desc src; OK key string value string Time taken: 0.148 seconds hive> select * from src; OK 238 val_238 Time taken: 0.107 seconds
建一个新的表create table src111(key bigint, value bigint);
insert数据到src111表中 insert into table src111 select * from src;
src的两个字段都是string,src111的两个表都是bigint,hive会做自动转换,通过UDFToLong这个udf自动把string转换成bigint,但是value值val_238无法转换成long 所以src111的值是:
hive> select * from src111; OK 238 0 Time taken: 0.107 seconds
UDFToLong在做类型转换时,如果string无法转换成long会得到NumberFormatException异常,但是这个异常没有被抛出。。。
} catch (NumberFormatException e) { // MySQL returns 0 if the string is not a well-formed numeric value. // return LongWritable.valueOf(0); // But we decided to return NULL instead, which is more conservative. return null; }