Martin,
Personally I would use a global temporary table in this scenario.
However if that is considered offensive or morally dubious, you could do
something like :
package pkg1
type t1 is table of mytable%rowtype index by binary_integer
g_t t1
g_i pls_integer
function f1 return pls_integer
g_t.delete
g_i := null
i := 1
for rec in (
select t.*, t.rowid
from mytable t
where ... for update
) loop
g_t(i) := rec
i := i + 1
delete from mytable where rowid = rec.rowid
end loop
return i
procedure p1(
i_subscript in pls_integer
,o_id out mytable.id%type
,o_created mytable.created%type)
if i_subscript between g_t.first and g_t.last then
o_id := g_t(i_subscript).id
o_created := g_t(i_subscript).created
end if
So, your perl code would call pkg1.f1 which would populate the package
level pl/sql table, delete the rows, and return the number of 'rows' in
that table. Your code would then call pkg1.p1 passing in the subscript
(1 .. n_rows).
Hope this helps,
Steve
On Wed, 2008-10-22 at 16:28 +0100, Martin Evans wrote:
> Hi,
>
> I am hoping someone might have had to do something like this and have a
> good solution. I am using DBD::Oracle. I have a table with a simple
> integer and a timestamp:
>
> create mytable (id int, created timestamp);
>
> The integer value may appear more than once and the timestamp is the
> timestamp when the row was created (it is actually created via a
> trigger). Other procedures write "id"s into the table at indeterminate
> times. The perl code wants to select the current distinct values of the
> "id" field, do something with them and then all rows which were present
> when the select was issued need to be deleted (since then more rows may
> have been added which must not be touched).
>
> This is easily achieved if I have two procs:
>
> PROCEDURE get(
> pdt OUT mytable.created%TYPE,
> pcur OUT SYS_REFCURSOR) AS
> BEGIN
> pdt := utc_timestamp();
> OPEN pcur FOR
> SELECT DISTINCT(id) FROM mytable WHERE created <= pdt;
> END;
>
> and:
>
> PROCEDURE delete(
> pdt IN mytable.created%TYPE,
> puid IN mytable.id%TYPE) AS
> BEGIN
> DELETE FROM mytable WHERE id = puid AND created <= pdt;
> END;
>
> Perl calls the first one to get the unique ids and the timestamp used to
> retrieve them, does something with the returned ids and then calls the
> second procedure one for each id to delete the rows. It does however,
> rely on the timestamp_format as if it is changed to remove milliseconds
> for instance the delete above may fail to find any rows (e.g. timestamp
> used was 2008-10-01 14:20:10.5555 but timestamp format omits the
> milliseconds then the timestamp pumped in to the second proc is
> 2008-10-01 14:20:10). As a result of this problem and it is 2 procs,
> this one ruled out.
>
> Ideally I'd like to achieve this in one procedure so I can guarantee no
> matter what happens in the perl the returned rows are deleted from the
> table. At first I thought that as the number of distinct ids will not be
> that many I could issue my select, loop through them putting them into
> an oracle table type, delete the rows in the real table then return the
> oracle table type to perl. However, DBD::Oracle does not support
> returning oracle table/array types other than via piped functions and as
> I found, you cannot issue a delete statement in a piped function e.g.,
> the following does not work:
>
> type mytype_t IS table of mytable.id%TYPE NOT NULL;
> type mytype_a IS TABLE OF mytable.id%TYPE NOT NULL
> INDEX BY BINARY_INTEGER;
>
> FUNCTION f_xxx RETURN mytable_t PIPELINED AS
> CURSOR cur(param_dt mytable.created%TYPE)
> IS SELECT DISTINCT(id) FROM mytable WHERE
> created <= param_dt;
> i integer := 1;
> dt mytable.created%TYPE;
> vu mytable_a;
> BEGIN
> dt := utc_timestamp();
> FOR row in cur(dt) LOOP
> vu(i) := row.id;
> i := i+1;
> END LOOP;
> -- following delete generates an error
> DELETE FROM mytable where created <= dt;
> FOR i in vu.first .. vu.last LOOP
> PIPE row(vu(i));
> END LOOP;
> END;
>
> The problem is returning multiple values from rows in a table back to
> perl and simultaneously deleting same rows. It can be achieved if I
> introduce a temporary table because the proc can select the rows into
> the temp table and delete the selected rows in the original table and
> the perl reads the temporary table but we try very hard to avoid
> temporary tables.
>
> If DBD::Oracle supported the return of oracle table types this would be
> easy.
>
> Anyone have any other ideas?
>
> Thanks
>
> Martin
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