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
|
Operator |
Symbol |
Notes |
|
equal |
== |
|
|
not equal |
!= |
|
|
less than |
< |
|
|
greater than |
> |
|
|
less than or equal to |
<= |
|
|
greater than or equal to |
>= |
|
|
pattern matching |
matches |
Takes an expression on the left and a string constant on the right. expression matches string-constant Use the Java format for regular expressions. |
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
|
bag |
tuple |
map |
int |
long |
float |
double |
chararray |
bytearray |
boolean |
datetime |
biginteger |
bigdecimal |
|
|
bag |
error |
error |
error |
error |
error |
error |
error |
error |
error |
error |
error |
error |
error |
|
tuple |
boolean (see Note 1) |
error |
error |
error |
error |
error |
error |
error |
error |
error |
error |
error |
|
|
map |
boolean (see Note 2) |
error |
error |
error |
error |
error |
error |
error |
error |
error |
error |
||
|
int |
boolean |
boolean |
boolean |
boolean |
error |
cast as boolean |
error |
error |
error |
error |
|||
|
long |
boolean |
boolean |
boolean |
error |
cast as boolean |
error |
error |
error |
error |
||||
|
float |
boolean |
boolean |
error |
cast as boolean |
error |
error |
error |
error |
|||||
|
double |
boolean |
error |
cast as boolean |
error |
error |
error |
error |
||||||
|
chararray |
boolean |
cast as boolean |
error |
error |
error |
error |
|||||||
|
bytearray |
boolean |
error |
error |
error |
error |
||||||||
|
boolean |
boolean |
error |
error |
error |
|||||||||
|
datetime |
boolean |
error |
error |
||||||||||
|
biginteger |
boolean |
error |
|||||||||||
|
bigdecimal |
boolean |
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)