[GitHub] [doris] BiteTheDDDDt commented on a diff in pull request #18565: [feature](function) Modified cast as time to behave more like MySQL

["BiteTheDDDDt (via GitHub)" <gi...@apache.org>]

BiteTheDDDDt commented on code in PR #18565:
URL: https://github.com/apache/doris/pull/18565#discussion_r1171057112


##########
be/src/vec/functions/function_cast.h:
##########
@@ -62,7 +65,91 @@ inline UInt32 extract_to_decimal_scale(const ColumnWithTypeAndName& named_column
     named_column.column->get(0, field);
     return field.get<UInt32>();
 }
+/** Cast from string or number to Time.
+  * In Doris, the underlying storage type of the Time class is Float64.
+  */
+struct TimeCast {
+    // Cast from string
+    // Some examples of conversions.
+    // '300' -> 00:03:00 '20:23' ->  20:23:00 '20:23:24' -> 20:23:24
+    template <typename T>
+    static bool try_parse_time(char* s, size_t len, T& x) {
+        char* first_char = s;
+        char* end_char = s + len;
+        int hour = 0, minute = 0, second = 0;
+        auto parse_from_str_to_int = [](char* begin, size_t len, auto& num) {
+            StringParser::ParseResult parse_result = StringParser::PARSE_SUCCESS;
+            auto int_value = StringParser::string_to_unsigned_int<uint64_t>(
+                    reinterpret_cast<char*>(begin), len, &parse_result);
+            if (UNLIKELY(parse_result != StringParser::PARSE_SUCCESS)) {
+                return false;
+            }
+            num = int_value;
+            return true;
+        };
+        char *first_colon {nullptr}, *second_colon {nullptr};
+        if ((first_colon = (char*)memchr(first_char, ':', len)) != nullptr) {

Review Comment:
   better use `If statements with initializer`
   if(x=y;x){
   }



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