> > On Wed, Aug 7, 2013 at 4:57 AM, Sameer Thakur <samthaku...@gmail.com>wrote: > >> Hello, >> 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 regards Sameer
