Re: SELECT FOR UPDATE

jose wrote:
> Hi all,
>
> I'm trying SELECT FOR UPDATE
> but I have a problem with locks.
>
> example:
> I have two users accessing to the same records, say...
>
> user1:
> DELECT * FROM table WHERE field=value FOR UPDATE
> ---------------------------------------------------------------------------
>
> user2:
> DELECT * FROM table WHERE field=value FOR UPDATE
> at this point user2 can't do nothing except waiting for user1 unlock recors.
>
> My question is:
>
> - Is it possible to know in advance if the records of a given query are
> locked, to prevent to be locked for ever?

Well, first of all the scientists are still unsure if this
universe will exist forever or not. So even if you find a way
to let your system survive the sun becoming a red giant and
so on, there's still uncertainty if it'll take forever or
not.

Anyway, the answer is no. Standard SQL doesn't have any
mechanism to check wether a given row is locked or to force a
query to fail with an error in the case a required lock isn't
available immediately.

But the question itself tells that you're about to implement
a major design error in your application. Holding database
locks during user interaction IS A BAD THING. Never, never
ever do it that way. And anybody telling you something
different is an overpaid idiot.

Jan

--

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# It's easier to get forgiveness for being wrong than for being right. #
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