github-actions[bot] commented on code in PR #68358:
URL: https://github.com/apache/doris/pull/68358#discussion_r4068253991
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be/src/exprs/function/function_regexp.cpp:
##########
@@ -178,10 +178,13 @@ struct RegexpExtractEngine {
results.emplace_back(matches[1].str());
}
if (matches[0].length() == 0) {
- if (search_start == search_end) {
+ // A zero-width match (e.g. a lookahead) may sit anywhere
after
+ // `search_start`, so step past the matched position
rather than
+ // the old start, otherwise the same position is matched
again.
+ if (matches[0].second == search_end) {
break;
}
- search_start += 1;
+ search_start = matches[0].second + 1;
Review Comment:
Moving the range start here resets Boost's match context, not just its scan
position. It drops the second capture for `regexp_extract_all('aa',
'(?<=(a))')` because the search at offset 2 cannot inspect the preceding `a`;
it skips Boost's required same-position consuming retry, so
`regexp_extract_all('xa', '((?<=x)|a)')` becomes `['']` instead of `['','a']`;
and it can invent anchored matches—for `xxa?b` with `(?<=a)|^(b)`, restarting
at `b` lets `^` capture in the middle of the original input. The array form
shares this loop. Please retain the original range and Boost's zero-length
progression (for example, use `boost::cregex_iterator`) and cover these
assertion/anchor cases in both result forms.
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