[
https://issues.apache.org/jira/browse/DERBY-4752?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Knut Anders Hatlen updated DERBY-4752:
--------------------------------------
Fix Version/s: 10.7.0.0
Issue & fix info: (was: [Patch Available])
I committed the 1c patch to trunk with revision 967000.
Lily: This class is only used for formatting timestamps when writing messages
to derby.log, so it's not part of normal query processing unless statement
logging is turned on. And even in the cases where logging is turned on, the 32%
slow-down is only for the generation of the timestamp, which is just a small
part of the total query cost, so the overall performance impact will probably
more like 1% than 30% (depending on the complexity of the query, of course). I
think that in environments where performance is critical, statement logging is
almost certainly turned off, and that's why I don't worry too much about it.
> CheapDateFormatter returns incorrect and invalid date strings
> -------------------------------------------------------------
>
> Key: DERBY-4752
> URL: https://issues.apache.org/jira/browse/DERBY-4752
> Project: Derby
> Issue Type: Bug
> Components: Services
> Affects Versions: 10.7.0.0
> Reporter: Knut Anders Hatlen
> Assignee: Knut Anders Hatlen
> Priority: Minor
> Fix For: 10.7.0.0
>
> Attachments: CheapFormatterPerfTest.java, derby-4752-1a.diff,
> derby-4752-1b.diff, derby-4752-1c.diff
>
>
> CheapDateFormatter has multiple problems. These are the ones I'm aware of:
> 1) On the boundary between non-leap years and leap years it will return first
> day of thirteenth month in previous year (for instance, 2011-13-01 instead of
> 2012-01-01)
> 2) It treats all years divisible by four as leap years. Those divisible by
> 100 and not by 400 are not leap years. It attempts to adjust for that (see
> the snippet below) but it always ends up setting leapYear=true if (year%4)==0.
> // It's a leap year if divisible by 4, unless divisible by 100,
> // unless divisible by 400.
> if ((year % 4L) == 0) {
> if ((year % 100L) == 0) {
> if ((year % 400L) == 0) {
> leapYear = true;
> }
> }
> leapYear = true;
> }
> 3) More leap year trouble. To find out which year it is, it calculates the
> number of four year periods that have elapsed since 1970-01-01. A four year
> period is considered 365*3+366 days. Although most four year periods are of
> that length, some are shorter, so we'll get one day off starting from year
> 2100, two days off from year 2200, and so on.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
