Re: gist access methods parameter types

Let me explain better what I want to do.
I want to have the types in sql level (composite types) like this:

--Spatio-Temporal Position in 3 Dimensions(cartessian x, cartessian y, time)
CREATE TYPE pos3d AS
(
x double precision,
y double precision,
t timestamp
);

--Spatio-Temporal Delta (comes from Δ, meaning alteration/change)
--i stands for (i)nitial position
--e stands for (e)nding position
--trajectory holds the id of the trajectory in which the current delta
belongs to
CREATE TYPE delta3d AS
(
i pos3d,
e pos3d,
trajectory integer
);

Having them in sql level eases my work much more than having them as base
types in C. But I need an index to speed up some operations. So I build two
types in C just for indexing purposes:

typedef struct {
float8 xi, yi;
Timestamp ti;
float8 xe, ye;
Timestamp te;
int32 trajectory;
} delta3d;

typedef struct {
float8 xl, yl;
Timestamp tl;
float8 xh, yh;
Timestamp th;
} delta3d_mbb;

As you see the first is a replica of my sql type in C and the second misses
some information (it is just the minimum bounding box which means that we
don't know initial/ending positions neither the trajectory id). The second
type is intended for non-leaf nodes while the first for leaf nodes.
My implementation of the tree is a kind of 3D-Rtree.
Now I am a little confused about the type of the arguments that each access
method (consistent, union, compress, decompress, penalty, picksplit, same)
requires in order to accomplish my goal.
Another black spot I have regarding compress.
If the entry passed to compress is a leaf entry then it is going to be of
sql type (composite type) delta3d (meaning I will get the values using
tuples etc). Correct? If not of what type is it going to be?
Assume it is a non-leaf entry. In that case of what type will it be? If it
is delta3d_mbb (C type) then I don't have to change it. But is it going to
be?
I am sorry if I seem importunate, but it has only been 2 weeks since I
started messing with postgresql C extensions, and I need help...