Re: Use array in a dynamic statement

I was wondering why USING clause is not supported in pl/pgsql dynamic statement. Serialization is the option I tried to avoid, but it seems there is no better approach available.

Just to say a few more about the usage of my function. In dag_tree_1, (rid, rtid) is the primary key, which identifies a node in a tree structure. The idx field is a kind of dewy index. for example:
rid rtid idx
1123 1 0000.0006.0033
3231 1 0000.0006
786 6 0000.0007.8853
80923 2 0000.0007.8853.2382

The function takes in a list of rid and rtid pair (nids), sort them by the length of the dewy index, which is equivalent to sort the nodes by their tree depth. That's what I try to achieve. Maybe someone has different idea to implement the function?

Thanks,
Sophie

----- Original Message ----
From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Sophie Yang <yangsophie(at)yahoo(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Sent: Thursday, March 5, 2009 12:06:24 AM
Subject: Re: [HACKERS] Use array in a dynamic statement

Hello

you can't to use parameters inside literal. There hasn't any sense (to
8.3, 8.4 will support USING).

you have to use serialisation to string and quoting.

some like

CREATE OR REPLACE FUNCTION foo(int[])
RETURNS SETOF int AS $$
DECLARE r record;
BEGIN
FOR r IN EXECUTE
'SELECT (' || quote_literal($1::text) ||
'::int[])[i] AS x
FROM generate_series(1, array_upper(' ||
quote_literal($1::text) || '::int[],1)) g(i)'
LOOP
RETURN NEXT r.x;
END LOOP;
RETURN;
END;
$$ LANGUAGE plpgsql;
SELECT * FROM foo(ARRAY[1,2,3]);

CREATE OR REPLACE FUNCTION foo84(int[])
RETURNS SETOF int AS $$
DECLARE r record;
BEGIN
FOR r IN EXECUTE
'SELECT $1[i] AS x FROM generate_series(1,
array_upper($1,1)) g(i)' USING $1
LOOP
RETURN NEXT r.x;
END LOOP;
RETURN;
END;
$$ LANGUAGE plpgsql;
SELECT * FROM foo84(ARRAY[1,2,3]);

regards
Pavel Stehule

2009/3/5 Sophie Yang <yangsophie(at)yahoo(dot)com>:
>
> Hi,
>
> I am trying to implement a PL/PgSQL function as following:
> CREATE OR REPLACE FUNCTION sort_by_d_idx (nids INT[][], tbl_name VARCHAR)
> RETURNS varchar[]
> AS $$
> DECLARE
> result varchar[];
> BEGIN
>
> EXECUTE 'SELECT ARRAY(SELECT t.idx FROM generate_series(array_lower($1,1), array_upper($1,1)) AS s(i), '
> ||tbl_name||' t WHERE $1[s.i][1] = t.rid and $1[s.i][2] = t.rtid ORDER BY length(t.idx))'
> INTO result;
>
> RETURN result;
> END;
> $$ LANGUAGE plpgsql;
>
> I got an error "ERROR: there is no parameter $1" when I test the function with:
> select sort_by_d_idx('{{8148, 1}, {8149, 1}, {300, 2}, {8163, 1}, {8170, 1}}'::int[][], 'd_tree_1');
>
> The error is understandable, but my question is how to supply the int[][] array into the dynamic SQL?
>
> To help understand the dynamic statement, the structure of d_tree_1 is (rid, rtid, idx). The PK is (rid, rtid) pair.
>
> If the tbl_name is fixed, the following function works well:
> CREATE OR REPLACE FUNCTION sort_by_d_idx2 (nids INT[][])
> RETURNS varchar[]
> LANGUAGE SQL
> AS $$
> SELECT ARRAY(
> SELECT t.idx
> FROM
> generate_series(array_lower($1,1), array_upper($1,1)) AS s(i), d_tree_1 t
> WHERE $1[s.i][1] = t.rid and $1[s.i][2] = t.rtid
> ORDER BY length(t.idx)
> );
> $$;
>
> Unfortunately, the tbl_name is determined at query time.
>
> Please help.
>
>
>
>
>
> --
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