[
https://issues.apache.org/jira/browse/DERBY-6834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14742507#comment-14742507
]
Rick Hillegas commented on DERBY-6834:
--------------------------------------
Note that CURRENT_TIME has the same optional precision argument, according to
the Standard. If we improve one, then I think that we should improve the other.
The 2011 SQL Standard, part 2, section 6.32 (datetime value function) has this
to say about the bounds and default for time and timestamp precisions:
SR 34) "If timePrecision is not specified, then 0 (zero) is implicit. If
timestampPrecision is not specified,
then 6 is implicit."
SR 36) "The maximum value of timePrecision and the maximum value of
timestampPrecision shall be the same implementation-defined value that is not
less than 6. The values of timePrecision and timestampPrecision shall not be
greater than that maximum value."
Derby violates SR 34 because the timestamp precision of
System.currrentTimeMillis() is 3. Changing this to 6 would create a backward
compatibility issue. Maybe it's a minor incompatibility since we are increasing
the precision rather than decreasing it.
We can't conform completely because these rules say that CURRENT_TIME and
CURRENT_TIMESTAMP must have the same maximum precision and that precision must
be at least microseconds. But a Derby TIME value is an instance of
java.sql.Time, which has millisecond precision.
If we pursue this enhancement, then I think that we should allow CURRENT_TIME
and CURRENT_TIMESTAMP to have different maximum precisions, the maximum
precison of CURRENT_TIMESTAMP should be 9 (the precision of System.nanoTime()),
and we should raise an error if the user specifies a precision which is out of
bounds.
Other thoughts?
Thanks,
-Rick
To conform to SR 36, we would need to raise an error if timestampPrecision is
greater than 9.
> support for CURRENT_TIMESTAMP(precision) appears to be missing
> --------------------------------------------------------------
>
> Key: DERBY-6834
> URL: https://issues.apache.org/jira/browse/DERBY-6834
> Project: Derby
> Issue Type: Improvement
> Reporter: Julian Reschke
> Attachments: firstTry.diff
>
>
> See
> <http://savage.net.au/SQL/sql-92.bnf.html#current%20timestamp%20value%20function>,
> <http://www.h2database.com/html/functions.html#current_timestamp>,
> <http://www.postgresql.org/docs/8.2/static/functions-datetime.html#FUNCTIONS-DATETIME-CURRENT>
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
