lo_copy()
I wonder if anyone has any comments on this [psuedo] code:
new loid := SELECT lo_creat(131072 + 262144);
UPDATE pg_largeobject SET
data = (SELECT data
FROM pg_largeobject
WHERE loid = <source loid> AND pageno = 0)
WHERE loid = <new loid> AND pageno = 0;
INSERT INTO pg_largeobject
(loid, pageno, data)
(SELECT <new loid>, pageno, data
FROM pg_largeobject
WHERE loid = <source loid> AND pageno > 0
);
It does seem to work but I wouldn't like to swear it's safe, hence this
posting.
I was originally looking for a newoid() function to use, then thought about
wrapping my own seeing as there wasn't one but then spotted there were some lo_
functions available. Therefore, lo_creat() I'm really just using to grab a new
oid for the new large object.
--
Nigel J. Andrews
"Nigel J. Andrews" <nandrews@investsystems.co.uk> writes:
I wonder if anyone has any comments on this [psuedo] code:
new loid := SELECT lo_creat(131072 + 262144);
UPDATE pg_largeobject SET
data = (SELECT data
FROM pg_largeobject
WHERE loid = <source loid> AND pageno = 0)
WHERE loid = <new loid> AND pageno = 0;
INSERT INTO pg_largeobject
(loid, pageno, data)
(SELECT <new loid>, pageno, data
FROM pg_largeobject
WHERE loid = <source loid> AND pageno > 0
);
I believe this will work, but it requires superuser privileges to
scribble on pg_largeobject directly. Probably would be better to go
through the gruntwork of creating a fully supported lo_copy() operation.
regards, tom lane
On Tue, 1 Apr 2003, Tom Lane wrote:
"Nigel J. Andrews" <nandrews@investsystems.co.uk> writes:
I wonder if anyone has any comments on this [psuedo] code:
new loid := SELECT lo_creat(131072 + 262144);
UPDATE pg_largeobject SET
data = (SELECT data
FROM pg_largeobject
WHERE loid = <source loid> AND pageno = 0)
WHERE loid = <new loid> AND pageno = 0;INSERT INTO pg_largeobject
(loid, pageno, data)
(SELECT <new loid>, pageno, data
FROM pg_largeobject
WHERE loid = <source loid> AND pageno > 0
);I believe this will work, but it requires superuser privileges to
scribble on pg_largeobject directly. Probably would be better to go
through the gruntwork of creating a fully supported lo_copy() operation.regards, tom lane
Thanks Tom, I was just a little worried that the page 0 record contained some
housekeeping type data that really shouldn't be copied from another page
0.
I noticed the scribbling on pg_largeobject priviledge and had created the
function with '...INVOKE AS DEFINER...' with a switch into superuser just for
that function's definition. Apart from making it more suitable for inclusion in
the main distribution, and possibly speed, I'm not sure what recoding in C
gives me given that I'm happy at the moment to do it this way. I may look into
a C version for submision later.
--
Nigel J. Andrews