Hi Sergei, I created this task based on our discussion: MDEV-8322 Distinguish between time and date strings more carefully Please also see comments below: On 06/15/2015 12:49 PM, Sergei Golubchik wrote:
Hi, Alexander!
On Jun 15, Alexander Barkov wrote:
(preference matters, as it tells how to parse ambiguous strings like "10:10:10").
I'd say '10:10:10' should be unambiguously treated as time. Colon is never used to delimit date parts. Is it?
yes, I believe delimiters are pretty much ignored in our code. so any delimiter can be used anywhere.
Right, in MariaDB they are ignored. But I mean in real life nobody uses colons to separate date parts.
Date parts are usually delimited by as follows: '01-01-01' '01.01.01' '01/01/01'
But this is a kind of separate issue. Would you like me to create a task for this?
The way it works now - after your patch - there's no much need for a "preference" flag. The only issue I've uncovered in testing was related to parsing strings with time preference. Like in
WHERE time_column > '2010-12-11'
The code is
my_bool str_to_time(const char *str, uint length, MYSQL_TIME *l_time, ulonglong fuzzydate, MYSQL_TIME_STATUS *status) { ... /* Check first if this is a full TIMESTAMP */ if (length >= 12) { /* Probably full timestamp */ (void) str_to_datetime(str, length, l_time, (fuzzydate & ~TIME_TIME_ONLY) | TIME_DATETIME_ONLY, status);
Which is very stupid, it decides solely on the string length. That is '2010-12-11' is parsed as a time (when there's time preference), but '10:11:12.123456' is parsed as a date (but fails and falls back to time).
I would suggest to get rid of this ad hoc detection code (check the length, try and fall back, etc). And use a systematic approach based on patterns. Like
patterns[]= { { 'yyyy-mm-dd' , parse_date }, { 'hh:mm:ss.uuuuuu', parse_time }, ... }
Note, I wrote "like". I do not mean literally these patterns or string patterns whatsoever. I'd prefer something much faster. May be some compact "signature" number that describes the format, or may be a decision tree (where the string is parsed into an array of ints and then analyzed like three numbers? first is 4 digit? etc).
Regards, Sergei