pig 的chararry类型不能用比较运算符comparison operator
pig 的chararry類型可能是按字段，逐個字段進行比較。
element_id 是chararray類型，
語句：
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'是錯誤的用法。
comparison operator不能操作chararray類型。
執行結果是 element_id為8 的被找出來了。‘8’>='14'，很奇怪啊！
而改成?element_id <='14'時，再執行時，
執行結果找到了element_id =‘1’和element_id =‘11’的，說明不行。
原理：估計是升級為bytearray，然后，按字段比較，逐個字段，所以，8>1，而1相同時，1<4
所以11小于14，而8大于14.
pig官網有說明：貌似只能用==和！=，兩邊不一致是，implicit cast支持從低到高，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)
轉載于:https://www.cnblogs.com/cl1024cl/p/6205409.html
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