Pluggable Storage Committed in Postgres

The result of the function must be a pointer to a struct of type , which contains everything that the core code needs to know to make use of the table access method. To implement a access method, an implementor will typically need to implement a AM specific type of tuple table slot (see ) which allows code outside the access method to hold references to tuples of the AM, and to access the columns of the tuple. One fairly large constraint of the table access method API is that, currently, if the AM wants to support modifications and/or indexes, it is necessary that each tuple has a tuple identifier ( ) consisting of a block number and an item number (see also Section 68.6).

Source: www.postgresql.org