Martin Simmons wrote:
>>>>>> On Thu, 16 Apr 2009 10:33:43 +0800, Craig Ringer said:
>> In the above, mtime is defined as a database `timestamp' rather than 
>> stored as the raw integer value from the source host. Note that the 
>> database may not store timestamps with the same precision as the fd 
>> host, and may store them using an internal floating-point form, so some 
>> error must be allowed for during verification.
> 
> Inaccuracy in mtime and ctime would break the accurate backups code.

It's sub-millisecond error. It just requires that comparisions for
equality be done in a similar way to floating-point comparisons, eg:

   a < b + err && a > b - err

which may or may not be a performance issue, but isn't a functional one.

It's one of the main things I want to look at, since for many other
purposes having usable timestamps in the database would be REALLY useful.

If it proves necessary to store binary-exact mtime and ctime values in
the DB, some job-level information on client timestamp format and
timezone might at least allow functions in the database to usefully
interpret these values (and, with functional indexes, search them
quickly albeit with an insert performance cost).

--
Craig Ringer

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