CURRENT OF cursor without OIDs

From: Ian Lance Taylor <ian(at)airs(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: CURRENT OF cursor without OIDs
Date: 2001-08-07 15:59:13
Message-ID: siae1bkgj2.fsf@daffy.airs.com
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Oracle PL/SQL supports a very convenient feature in which you can say
something like
DECLARE
CURSUR cur IS SELECT * FROM RECORD;
BEGIN
OPEN cur;
UPDATE record SET field = value WHERE CURRENT OF cur;
CLOSE cur;
END

We have cursors in the development version of PL/pgSQL, but they don't
support CURRENT OF. In the patch I wrote a few months back to add
cursor support to PL/pgSQL, which was not adopted, I included support
for CURRENT OF. I did it by using OIDs. Within PL/pgSQL, I modified
the cursor select statement to also select the OID. Then I change
WHERE CURRENT OF cur to oid = oidvalue. Of course this only works in
limited situations, and in particular doesn't work after OID
wraparound.

Anyhow, I see that there is a move afoot to eliminate mandatory OIDs.
My question now is: if there is no OID, is there any comparable way to
implement CURRENT OF cursor? Basically what is needed is some way to
identify a particular row between a SELECT and an UPDATE.

Ian

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