help using arrays in a function

[Jennifer Lee]

Hello,

I have a rather simple function I've been using in 7.3.4

version
------------------------------------------------------------------------
-----------------
PostgreSQL 7.3.4 on i686-pc-cygwin, compiled by GCC gcc (GCC) 3.2
20020927 (prerelease)
(1 row)

This compares an integer to all elements in an integer array and looks
for a match

CREATE OR REPLACE FUNCTION public.array_element_compare(_int4, int4)
RETURNS text AS
'
DECLARE
a ALIAS FOR $1;
b ALIAS FOR $2;
i integer;
status text;
BEGIN
i := 1;
status := ''false'';
WHILE a[i] LOOP
IF a[i] = b THEN
status := ''true'';
END IF;
i := i+1;
END LOOP;
RETURN status;
END;'
LANGUAGE 'plpgsql';

It works find

germinate1.5 =# select array_element_compare('{100,92,82}', 82);
array_element_compare
-----------------------
true
(1 row)

germinate1.5 =# select array_element_compare('{100,92}', 82);
array_element_compare
-----------------------
false
(1 row)

I'm now testing our database on 7.4 and get an error with this function
and I can't figure out how to fix it.

version
------------------------------------------------------------------------
-------------
PostgreSQL 7.4 on i686-pc-cygwin, compiled by GCC gcc (GCC) 3.3.1
(cygming special)
(1 row)

germinate1.5 =# select array_element_compare('{100, 92, 82}', 82);
ERROR: invalid input syntax for type boolean: "100"
CONTEXT: PL/pgSQL function "array_element_compare" line 9 at while

Can anyone point me in the right direction?

Thanks much for any help,
Jennifer



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[Tom Lane]

"Jennifer Lee" <jl**@scri.sari.ac.uk> writes:

WHILE a[i] LOOP I'm now testing our database on 7.4 and get an error with this function
and I can't figure out how to fix it.
ERROR: invalid input syntax for type boolean: "100"
CONTEXT: PL/pgSQL function "array_element_compare" line 9 at while

plpgsql now enforces that the test expression of IF, WHILE, etc must be
a boolean. The above is not.

This is pretty poor coding practice anyway, since even before 7.4 it
would have given wrong answers for arrays containing zeroes or arrays
whose lower index bound is not 1. I'd suggest using the array_lower and
array_upper functions to determine the valid range of subscripts.
Something like

FOR i IN array_lower(a,1) .. array_upper(a,1) LOOP

should work.

regards, tom lane

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[Joe Conway]

Jennifer Lee wrote:

WHILE a[i] LOOP

This problem has nothing to do with arrays, per se. PL/pgSQL no longer
assumes it can coerce an integer constant to a boolean. Instead make the
above line look like this:

WHILE a[i] IS NOT NULL LOOP
BTW, in 7.4 you could more easily get the same result like this:

regression=# select 82 = any ('{100,92,82}');
?column?
----------
t
(1 row)

regression=# select 82 = any ('{100,92}');
?column?
----------
f
(1 row)

See:
http://www.postgresql.org/docs/curre...mparisons.html

HTH,

Joe

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