How to pass table name to plpgsql function - postgresql

Question

I am trying to run the code:
CREATE OR REPLACE FUNCTION anly_work_tbls.testfncjh (tablename text) returns int
AS $$
DECLARE
counter int;
rec record;
tname text;
BEGIN
counter = 0;
tname := tablename;
FOR rec IN
select *
from tname
loop
counter = counter + 1;
end loop;
RETURN counter;
END;
$$
LANGUAGE 'plpgsql' IMMUTABLE
SECURITY DEFINER;
The goal of this code is to return the number of rows in the table you input. I know that this might not be the best way to accomplish this task, but the structure of this function would extend nicely to another question I am trying to tackle. Every time I run the code, I get the error:
ERROR: syntax error at or near "$1"
All online resources I have found tell me how to use the input variable within and EXECUTE block, but not in the above situation.
Currently running PostgreSQL 8.2.15.

Answer 1

CREATE OR REPLACE FUNCTION anly_work_tbls.testfncjh (tbl regclass, OUT row_ct int) AS
$func$
BEGIN
EXECUTE 'SELECT count(*) FROM '|| tbl
INTO row_ct;
END
$func$ LANGUAGE plpgsql IMMUTABLE SECURITY DEFINER;
Call:
SELECT anly_work_tbls.testfncjh('anly_work_tbls.text_tbl');
This should work for Postgres 8.2, but you consider upgrading to a current version anyway.
I pass the table name as object identifier type regclass, which takes care of quoting automatically and works with schema-qualified names. Details:
Table name as a PostgreSQL function parameter
Using an OUT parameter simplifies the function.
Don't quote the language name. It's an identifier.
If you actually need to loop through the result of a dynamic query:
CREATE OR REPLACE FUNCTION anly_work_tbls.testfncjh (tbl regclass)
RETURNS int AS
$func$
DECLARE
counter int := 0; -- init at declaration time
rec record;
BEGIN
FOR rec IN EXECUTE
'SELECT * FROM ' || tbl
LOOP
counter := counter + 1; -- placeholder for some serious action
END LOOP;
RETURN counter;
END
$func$ LANGUAGE plpgsql IMMUTABLE SECURITY DEFINER;
Read this chapter in the manual: Looping Through Query Results
The documented assignment operator in plpgsql is :=:
The forgotten assignment operator "=" and the commonplace ":="

Answer 2

Yes is really not the best way, but this would work:
CREATE OR REPLACE FUNCTION testfncjh (tablename text) returns int
AS $$
DECLARE
counter int;
rec record;
BEGIN
counter = 0;
FOR rec IN
EXECUTE 'select * from '||quote_ident(tablename) loop
counter = counter + 1;
end loop;
RETURN counter;
END;
$$
LANGUAGE 'plpgsql' IMMUTABLE
SECURITY DEFINER;
This would be nicer:
CREATE OR REPLACE FUNCTION testfncjh (tablename text) returns int
AS $$
DECLARE _count INT;
BEGIN
EXECUTE 'SELECT count(*) FROM '|| quote_ident(tablename) INTO _count;
RETURN _count;
END;
$$
LANGUAGE 'plpgsql' IMMUTABLE
SECURITY DEFINER;