I wanted to create a composite datatype to represent a Node. So it would have a few attributes and an array of type Node which is the children of this node.
create type Node as (r integer, s integer, children Node []);
But i get error type Node[] does not exist. I understand that Node is not defined hence the error.
But how do i get around this problem?
What exactly are you trying to accomplish? I can think of a number of ways.
For example, suppose we have a table like:
create table node (
id int primary key,
parent int references node(id),
content text not null
);
We could create a function like this:
CREATE FUNCTION children(node) RETURNS node[] LANGUAGE SQL AS
$$
SELECT array_agg(node) FROM node WHERE parent=$1.id;
$$;
Then we could still do:
select n.children FROM node n WHERE id = 123;
Note that causes two separate scans, but should work.
Thank you.
I am trying to capture plan statistics for every node in the plan tree. For this i have plan view which has plan specific information like planid,plan_text, and root_node of type Node.
Type Node has node specific statistics like estimated_startup_cost, estimated_actual_cost etc. It also has child_nodes of type Node[]. i face the problem of self referencing composite type in defining Node type.
The reason i wanted a type Node is because while initializing memory for my contrib module i have GUC parameter specifying max number of Nodes. I was thinking that it is possible to initialize memory with a sizeof(Node).
Still trying to figure out how using a table storing Node will help me in figuring out how much initial memory can be allocated
