We need to distinguish better between date ad time strings when parsing strings in str_to_date(), str_to_time(), etc.
Hi, Alexander!
On Jun 15, Alexander Barkov wrote:
>> (preference matters, as it tells how to parse ambiguous strings like
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>> "10:10:10").
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>
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> I'd say '10:10:10' should be unambiguously treated as time.
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> Colon is never used to delimit date parts. Is it?
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yes, I believe delimiters are pretty much ignored in our code. so any
delimiter can be used anywhere.
> Date parts are usually delimited by as follows:
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> '01-01-01'
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> '01.01.01'
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> '01/01/01'
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>
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> But this is a kind of separate issue. Would you like me to create a task
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> for this?
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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'
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The code is
my_bool str_to_time(const char *str, uint length, MYSQL_TIME *l_time,
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ulonglong fuzzydate, MYSQL_TIME_STATUS *status)
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{
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...
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/* Check first if this is a full TIMESTAMP */
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if (length >= 12)
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{ /* Probably full timestamp */
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(void) str_to_datetime(str, length, l_time,
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(fuzzydate & ~TIME_TIME_ONLY) | TIME_DATETIME_ONLY,
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status);
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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[]=
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{
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{ 'yyyy-mm-dd' , parse_date },
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{ 'hh:mm:ss.uuuuuu', parse_time },
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...
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}
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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).