How can i get record by data block not by sql?

How can i get record by data block not by sql?
I want to read and write lots of data by data blocks and write a record to a appointed data blocks,so i can form a disk-resident tree by recording the block address. But i don't know how to implement in postgresql.
Is there system function can do this?
Can someone help me?? Thank you very very much!!!!1

Please don't cross-post. Responding on -hackers because it seems a
better fit here than on -performance.

"姜头" <104186179(at)qq(dot)com> wrote:

> How can i get record by data block not by sql?
>
> I want to read and write lots of data by data blocks and write
> record to a appointed data block and read it. so i can form a
> disk-resident tree by recording the block address. But i don't
> know how to implement in postgresql.
> Is there system function can do this?

It's not really clear what you want to do, why you want parts of
PostgreSQL involved, or why you want to bypass other parts of
PostgreSQL.

That said, I think you might want to start reading source code and
README files. You might find something in the contrib area which
could make a good example. An FDW might be exactly what you want,
or the exact opposite of what you want -- I really can't tell from
the sketchy information provided.

-Kevin