Re: Changing isolation level?

NoJunkMailshah_at_xnet.com wrote:
> While stranded on information super highway D Alpern wrote:
> :)SELECT... FOR UPDATE {WAIT | NOWAIT} springs to mind...
> :)
>
> No, you cannot select for update when you just want to read the data, it
> will lock out everyone else.

But locking everyone else out is exactly what you want to happen.

situation 1) T1 deletes row A, a microsecond later T2 selects row A.

situation 2) T2 selects row A, a microsecond later T1 deletes row A.

Are you saying that in situation 1 you want T2 to block, but in situation 2 you don't want T1 to block? Assuming T1 and T2 are independent transactions, this is logically incoherent. If integrity requires that one situation needs to block, then so does the other situation. No?

Xho

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