lriggs commented on code in PR #50187:
URL: https://github.com/apache/arrow/pull/50187#discussion_r3686938563
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cpp/src/gandiva/precompiled/string_ops.cc:
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@@ -1948,9 +1956,55 @@ const char* replace_utf8_utf8_utf8(gdv_int64 context,
const char* text,
gdv_int32 text_len, const char* from_str,
gdv_int32 from_str_len, const char* to_str,
gdv_int32 to_str_len, gdv_int32* out_len) {
+ // Size the output buffer so large results are not capped by an arbitrary
+ // limit, while avoiding a second pass over the input in the common case.
+ // - No replacement possible, or the result can only shrink/stay equal:
+ // text_len is a safe exact-or-upper bound, no scan.
+ // - Small expansion (replacement at most ~2x the match): use an O(1) upper
+ // bound that assumes every position matches. This over-allocates by at
+ // most ~text_len bytes but skips the match-counting scan entirely.
+ // - Large expansion: that upper bound could be many times the input for
+ // sparse matches, so count non-overlapping matches for the exact size.
+ gdv_int64 max_length;
+ if (from_str_len <= 0 || from_str_len > text_len || to_str_len <=
from_str_len) {
+ max_length = text_len;
+ } else {
+ gdv_int32 delta = to_str_len - from_str_len; // > 0
+ gdv_int64 upper_bound = static_cast<gdv_int64>(text_len) +
+ (static_cast<gdv_int64>(text_len) / from_str_len)
* delta;
+ if (delta <= from_str_len && upper_bound <= INT_MAX) {
Review Comment:
good point. I updated this to a lower limit.
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