Re: updateable cursors & visibility - Mailing list pgsql-hackers

From Peter Eisentraut
Subject Re: updateable cursors & visibility
Date
Msg-id Pine.LNX.4.44.0303271011280.2228-100000@peter.localdomain
Whole thread Raw
In response to Re: updateable cursors & visibility  (Bruce Momjian <pgman@candle.pha.pa.us>)
Responses Re: updateable cursors & visibility  (Bruce Momjian <pgman@candle.pha.pa.us>)
List pgsql-hackers
Bruce Momjian writes:

> One idea is to require FOR UPDATE on the cursor --- while that prevents
> other transactions from changing the cursor, it doesn't deal with the
> current transaction modifying the table outside the cursor.

That would only keep existing rows from being deleted but not new rows
from being added.

> One idea is
> to have UPDATE/DELETE WHERE CURRENT OF behave like UPDATE/DELETE do now
> when they find a row that is locked by another transaction --- they wait
> to see if the transaction commits or aborts, then if committed they
> follow the tid to the newly updated row, check the WHERE clause to see
> if it still is satisfied, then perform the update.  (Is this correct?)

Surely it would have to do something like that, but that's a matter of the
transaction isolation, not the sensitivity.  It doesn't do anything to
address the potential problems I mentioned.

-- 
Peter Eisentraut   peter_e@gmx.net



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