pig 的chararry类型不能用比较运算符comparison operator

pig 的chararry类型可能是按字段，逐个字段进行比较。

element_id 是chararray类型，

语句：

no_app_category_mapping = filter no_element_id by element_id == ‘‘ or element_id is null or element_id == ‘0‘ or element_id >=‘14‘;

其中，element_id >=‘14‘是错误的用法。

comparison operator不能操作chararray类型。

执行结果是 element_id为8 的被找出来了。‘8’>=‘14‘，很奇怪啊！

而改成 element_id <=‘14‘时，再执行时，

执行结果找到了element_id =‘1’和element_id =‘11’的，说明不行。

原理：估计是升级为bytearray，然后，按字段比较，逐个字段，所以，8>1，而1相同时，1<4

所以11小于14，而8大于14.

pig官网有说明：貌似只能用==和！=，两边不一致是，implicit cast支持从低到高，不支持高到低。

如下：

Comparison Operators

Description

Use the comparison operators with numeric and string data.

Examples

Numeric Example

X = FILTER A BY (f1 == 8);

String Example

X = FILTER A BY (f2 == ‘apache‘);

Matches Example

X = FILTER A BY (f1 matches ‘.*apache.*‘);

Types Table: equal (==) operator

Note 1: boolean (Tuple A is equal to tuple B if they have the same size s, and for all 0 <= i < s A[i] == B[i])

Note 2: boolean (Map A is equal to map B if A and B have the same number of entries, and for every key k1 in A with a value of v1, there is a key k2 in B with a value of v2, such that k1 == k2 and v1 == v2)