js8544 commented on code in PR #33806:
URL: https://github.com/apache/arrow/pull/33806#discussion_r1083265094
##########
cpp/src/arrow/compute/kernels/scalar_string_ascii.cc:
##########
@@ -1505,6 +1508,13 @@ struct MatchLike {
static const RE2 kLikePatternIsStartsWith(R"(([^%_]*[^\\%_])?%+)",
kRE2Options);
// A LIKE pattern matching this regex can be translated into a suffix
search.
static const RE2 kLikePatternIsEndsWith(R"(%+([^%_]*))", kRE2Options);
+ static bool global_checked = false;
+ if (ARROW_PREDICT_FALSE(!global_checked)) {
+ RETURN_NOT_OK(RegexStatus(kLikePatternIsSubstringMatch));
+ RETURN_NOT_OK(RegexStatus(kLikePatternIsStartsWith));
+ RETURN_NOT_OK(RegexStatus(kLikePatternIsEndsWith));
Review Comment:
I think it does though. `global_checked` is set to true only if all three
patterns are ok.
##########
cpp/src/arrow/compute/kernels/scalar_string_ascii.cc:
##########
@@ -1505,6 +1508,13 @@ struct MatchLike {
static const RE2 kLikePatternIsStartsWith(R"(([^%_]*[^\\%_])?%+)",
kRE2Options);
// A LIKE pattern matching this regex can be translated into a suffix
search.
static const RE2 kLikePatternIsEndsWith(R"(%+([^%_]*))", kRE2Options);
+ static bool global_checked = false;
Review Comment:
I also feel like a static boolean is enough for our case. As it avoids false
positives, i.e., erroneous regexes are always checked.
##########
cpp/src/arrow/compute/kernels/scalar_string_ascii.cc:
##########
@@ -1505,6 +1508,13 @@ struct MatchLike {
static const RE2 kLikePatternIsStartsWith(R"(([^%_]*[^\\%_])?%+)",
kRE2Options);
// A LIKE pattern matching this regex can be translated into a suffix
search.
static const RE2 kLikePatternIsEndsWith(R"(%+([^%_]*))", kRE2Options);
+ static bool global_checked = false;
Review Comment:
I thought about using `std::call_once` but the only solution I can come up
with uses exceptions:
```cpp
static std::once_flag global_checked;
try {
std::call_once(global_checked, [] {
auto check_global = [] {
RETURN_NOT_OK(RegexStatus(kLikePatternIsSubstringMatch));
RETURN_NOT_OK(RegexStatus(kLikePatternIsStartsWith));
RETURN_NOT_OK(RegexStatus(kLikePatternIsEndsWith));
};
auto status = check_global();
if (!status.ok()) { // throw an exception so that once_flag is not
set
throw std::invalid_argument(status.ToString());
}
});
} catch (const std::invalid_argument& e) {
return Status::Invalid(e.what());
}
```
I couldn't find a more elegant solution. WDYT?
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