Composite Index Structure

Hi all,<br /><br />I want to construct an "Composite Index Structure" i.e. a combination of gist and btree. <br />What
iam thinking is that first creating a Rtree structure that is pointing to another Btree structure.<br /> For example,
Supposei want to find vehicles between 2 to 4 pm on 14/2/2011 on X road.<br /><br />I am thinking of creating rtree
structurefor road network and then btree for time. For reaching X road i use Rtree, and from there btree begin i.e.
leafnode of rtree contains the pointer to root node of btree ( in this way i have all time belonging to X road) <br
/><br/>My question is that how to implement this composite index structure in postgres?<br /><br />Let us suppose, if i
createmygist index, then i have to write my own operator class?<br />or <br />can i use gist index as it is and btree
treeas it is. I mean their operator class and their gist methods but how to establish linkage between them?<br /><br
/>Anyidea ??<br /><br />Thanks<br /><font color="#888888">Raj</font>