Re: text -> time cast problem

[2001-12-06 13:00] Tom Lane said:
| Brent Verner <brent(at)rcfile(dot)org> writes:
| > [2001-12-04 18:15] Tom Lane said:
| > | But you are definitely right that
| > |
| > | time '17:12:28.123'
|
| > sql-99 seems to contradict this assertion.
| > page 160 (Syntax Rules, 6.1 <data type>)
|
| > 30) If <time precision> is not specified, then 0 (zero) is implicit.
| > If <timestamp precision> is not specified, then 6 is implicit.
|
| But that's <data type>, ie, they're specifying the implied width of
| a table column that's declared "foo time". The rules for <time literal>
| are different.

Understood now.

I'd misunderstood the meaning of "if specified" in the <time literal>
definition; specifically, I interpreted it as "if specified by
<time precision>" as opposed to the intended meaning of "if specified
in <time string>"... so off I went seeking additional definitions
to support treating "TIME <time string>" as "TIME(0) <time string>"...

Thanks for swinging the clue stick my way :-)

| Our problem is that we want to generalize the notion of <time literal>
| to be <datatype> <string literal>, and this makes it hard to have
| datatype-specific rules that differ from the rules that apply in the
| column-datatype context.
|
| My thought is that we should resolve this conflict by rejecting the
| part of the spec that assigns fixed default precisions to time
| and timestamp columns, the same as we have done for type numeric.
| There's no benefit to the user in that requirement; it's only a
| crutch for implementations that cannot cope with variable-width
| columns effectively. If people want a column that rounds fractional
| inputs to integral seconds, let 'em say "TIME(0)". But I don't
| think that "TIME" should do so, especially when the spec provides
| no alternative way to get the effect of "time with no particular
| precision restriction". It's the old "text vs varchar(N)" game all
| over again.

This seems fair. Would this approach imply that CURRENT_TIME and
CURRENT_TIMESTAMP should not apply default precision to their return
values? Right now, "CURRENT_TIME" is equivalent to "CURRENT_TIME(0)"
and "CURRENT_TIMESTAMP" eq to "CURRENT_TIMESTAMP(6)".

cheers.
brent

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