Why is that Strange Behaviour with SETOF in PostgreSQL? - database

Question

I have the following Code Snippets{ CODE#1 , CODE#2, CODE #3 } In my Database.
CODE #1 : Create Statement of a Table "Class_Type" which is like a "ENUM in JAVA".
It Contains some data as { "class-A", 'class-B", "sports-A", "RED", "BLUE",.....}
Now i am trying to fetch these values using a Stored Procedure which is CODE#2 and CODE#3.
Expected Output of CODE#2 and CODE#3 :
{
| classtype character varying |
| class-A |
| class-B |
| sports-A |
| RED |
| BLUE |
| ....... |
}
What did i find Strange?
The CODE#2 is returning the Expected Output some times and some times it returns "Unexpected output". What is the Reason behind ?
The Code#3 is working fine and resulting the Expected Output Every Time.
Unexpected Output of CODE#2 :
{
| get_class_type_list character varying |
| class-A |
| class-B |
| sports-A |
| RED |
| BLUE |
| ....... |
}
Following are the Code Snippets :
CODE#1
{
CREATE TABLE test.class_type
(
value character varying(80) NOT NULL,
is_active boolean NOT NULL DEFAULT true,
sort_order integer,
CONSTRAINT class_type_pkey PRIMARY KEY (value)
)
WITH (
OIDS=FALSE
);
}
CODE#2
{
CREATE OR REPLACE FUNCTION test.get_class_type_list()
RETURNS SETOF character varying AS
$BODY$
DECLARE
SQL VARCHAR;
BEGIN
RETURN QUERY
(SELECT value AS "classType"
FROM TEST.CLASS_TYPE);
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
ROWS 1000;
}
CODE#3
{
CREATE OR REPLACE FUNCTION test.get_class_type_list()
RETURNS TABLE(classType character varying) AS
$BODY$
DECLARE
SQL VARCHAR;
BEGIN
RETURN QUERY
(SELECT value AS "classType"
FROM TEST.CLASS_TYPE);
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
ROWS 1000;
}
SQL Fiddle Sample Code
Edited:
I want the column name of the Return Function to be as "classType", but not the function name.

Answer 1

The only difference I see in the results, is the column name (which is actually an alias). You have full control over column aliases at the calling context: sqlfiddle (and the reason, sometimes it behaves differently, it's because RETURNS SETOF <primitive-type> is a special returning clause).
The rule of thumb is, if you have alias in the function definition (like OUT parameters, RETURNS TABLE & RETURNS SETOF <composite/row-type>; but not in the function body itself), postgresql will use that, unless there is an explicit alias. If you use RETURNS SETOF <primitive/simple-type> without OUT parameters, the default alias is the function name for that column.
Note: the reason behind I didn't post this as an answer the first time, is because unfortunately, I couldn't find any reference for this in the docs.