morningman commented on a change in pull request #3345: [FIX] fix doris string
functions not support multibyte string
URL: https://github.com/apache/incubator-doris/pull/3345#discussion_r410261854
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File path: be/src/exprs/string_functions.cpp
##########
@@ -37,19 +37,55 @@ void StringFunctions::init() {
// - supported negative positions (count from the end of the string)
// - [optional] len. No len indicates longest substr possible
StringVal StringFunctions::substring(
- FunctionContext* context, const StringVal& str,
+ FunctionContext* context, const StringVal& str,
const IntVal& pos, const IntVal& len) {
if (str.is_null || pos.is_null || len.is_null) {
return StringVal::null();
}
+ if (len.val <= 0 || str.len == 0) {
+ return StringVal();
+ }
+
+ // create index indicate every char start byte
+ // e.g. "hello word 你好" => [0,1,2,3,4,5,6,7,8,9,10,11,14] 你 and 好 are 3
bytes
+ // why use a vector as index? if theres is no negative pos val it is
unnecessary,
+ // but if has pos is negative it is not easy to determin where to start,
so need a
+ // index save ervery charactor's length
Review comment:
```suggestion
// index save every character's length
```
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