From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Manfred Koizar <mkoi-pg(at)aon(dot)at>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Aaron Held <aaron(at)MetroNY(dot)com>, Roberto Mello <rmello(at)cc(dot)usu(dot)edu>, Neil Conway <neilc(at)samurai(dot)com>, pgsql-sql(at)postgresql(dot)org |
Subject: | Re: [GENERAL] CURRENT_TIMESTAMP |
Date: | 2002-09-23 20:36:59 |
Message-ID: | 200209231336.59105.josh@agliodbs.com |
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Lists: | pgsql-general pgsql-hackers pgsql-sql |
Manfred,
> C2: The returned value has to represent a point in time *during* the
> execution of the SQL-statement.
>
> The only thing an implementor is free to choose is which point in time
> "during the execution of the SQL-statement" is to be returned, i.e. a
> timestamp in the interval between the start of the statement and the
> first time when the value is needed.
>
> The current implementation only conforms to C1.
I, for one, would judge that the start time of the statement is "during the
execution"; it would only NOT be "during the execution" if it was a value
*before* the start time of the statement. It's a semantic argument.
The spec is, IMHO, rather vague on how this would relate to transactions. I
do not find it at all inconsitent that Bruce, Thomas, and co. interpreted a
transaction to be an extension of an individual SQL statement for this
purpose (at least, that's what I guess they did).
Thus, if you accept the postulates that:
1) "During" a SQL statement includes the start time of the statement, and
2) A Transaction is the equivalent of a single SQL statement for many
purposes,
Then the current behavior is a logical conclusion.
Further, we could not change that behaviour without breaking many people's
applications.
Ideally, since we get this question a lot, that a compile-time or
execution-time switch to change the behavior of current_timestamp
contextually would be nice. We just need someone who;s interested enough in
writing one.
--
-Josh Berkus
Aglio Database Solutions
San Francisco
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