8.3 PLpgSQL Can't Compare Records?

On Wed, Jul 1, 2009 at 1:35 PM, David E. Wheeler<david@kineticode.com> wrote:

This code:

   CREATE OR REPLACE FUNCTION foo() returns boolean as $$
   DECLARE
       have_rec record;
       want_rec record;
   BEGIN
       have_rec := row(1, 2);
       want_rec := row(3, 5);
       RETURN have_rec IS DISTINCT FROM want_rec;
   END;
   $$ language plpgsql;

   SELECT ROW(1, 2) IS DISTINCT FROM ROW(3, 5);

   SELECT foo();
   DROP FUNCTION foo();

Works as expected on 8.4, outputting:

    ?column?
   ----------
    t
   (1 row)

   Time: 48.626 ms
    foo
   -----
    t
   (1 row)

On 8.3, however, the row comparisons in the SQL statement works, but fails
in the PL/pgSQL function, with this output:

    ?column?
   ----------
    t
   (1 row)

   psql:huh.sql:14: ERROR:  operator does not exist: record = record
   LINE 1: SELECT   $1  IS DISTINCT FROM  $2
                        ^
   HINT:  No operator matches the given name and argument type(s). You might
need to add explicit type casts.
   QUERY:  SELECT   $1  IS DISTINCT FROM  $2
   CONTEXT:  PL/pgSQL function "foo" line 7 at RETURN

Is this a known issue in 8.3? If so, is there a known workaround?

fyi: works in 8.4, as part of a broad fix of composite type comparison ops

merlin

On Wed, Jul 1, 2009 at 2:45 PM, Merlin Moncure<mmoncure@gmail.com> wrote:

On Wed, Jul 1, 2009 at 1:35 PM, David E. Wheeler<david@kineticode.com> wrote:

This code:

   CREATE OR REPLACE FUNCTION foo() returns boolean as $$
   DECLARE
       have_rec record;
       want_rec record;
   BEGIN
       have_rec := row(1, 2);
       want_rec := row(3, 5);
       RETURN have_rec IS DISTINCT FROM want_rec;
   END;
   $$ language plpgsql;

   SELECT ROW(1, 2) IS DISTINCT FROM ROW(3, 5);

   SELECT foo();
   DROP FUNCTION foo();

Works as expected on 8.4, outputting:

    ?column?
   ----------
    t
   (1 row)

   Time: 48.626 ms
    foo
   -----
    t
   (1 row)

On 8.3, however, the row comparisons in the SQL statement works, but fails
in the PL/pgSQL function, with this output:

    ?column?
   ----------
    t
   (1 row)

   psql:huh.sql:14: ERROR:  operator does not exist: record = record
   LINE 1: SELECT   $1  IS DISTINCT FROM  $2
                        ^
   HINT:  No operator matches the given name and argument type(s). You might
need to add explicit type casts.
   QUERY:  SELECT   $1  IS DISTINCT FROM  $2
   CONTEXT:  PL/pgSQL function "foo" line 7 at RETURN

Is this a known issue in 8.3? If so, is there a known workaround?

fyi: works in 8.4, as part of a broad fix of composite type comparison ops

whoops, you knew that already :-). one possible workaround is:

select $1::text is distinct from $2::text;

merlin

On Jul 1, 2009, at 11:47 AM, Merlin Moncure wrote:

fyi: works in 8.4, as part of a broad fix of composite type
comparison ops

whoops, you knew that already :-). one possible workaround is:

select $1::text is distinct from $2::text

Yes, and that's what I'm doing, although it is significantly less
precise, in that:

* Columns with different types may successfully compare (e.g., NULL
and '')
* No (easy) way to tell if two records have different numbers of columns

But it's good enough for 8.3 if there is no other workaround.

Thanks,

David

David E. Wheeler wrote:

This code:

CREATE OR REPLACE FUNCTION foo() returns boolean as $$
DECLARE
have_rec record;
want_rec record;
BEGIN
have_rec := row(1, 2);
want_rec := row(3, 5);
RETURN have_rec IS DISTINCT FROM want_rec;
END;
$$ language plpgsql;

SELECT ROW(1, 2) IS DISTINCT FROM ROW(3, 5);

SELECT foo();
DROP FUNCTION foo();

Works as expected on 8.4, outputting:

[...]

On 8.3, however, the row comparisons in the SQL statement works, but
fails in the PL/pgSQL function, with this output:

?column?
----------
t
(1 row)

psql:huh.sql:14: ERROR: operator does not exist: record = record
LINE 1: SELECT $1 IS DISTINCT FROM $2
^
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
QUERY: SELECT $1 IS DISTINCT FROM $2
CONTEXT: PL/pgSQL function "foo" line 7 at RETURN

Is this a known issue in 8.3? If so, is there a known workaround?

The change is probably here:
http://archives.postgresql.org/pgsql-committers/2008-10/msg00110.php

So I think it is safe to argue that this is not a bug in 8.3, but an improvement in 8.4.

Yours,
Laurenz Albe

On Jul 7, 2009, at 12:49 AM, Albe Laurenz wrote:

Is this a known issue in 8.3? If so, is there a known workaround?

The change is probably here:
http://archives.postgresql.org/pgsql-committers/2008-10/msg00110.php

So I think it is safe to argue that this is not a bug in 8.3, but an
improvement in 8.4.

Right, good find, thanks.

David