pg_am stores information about
relation access methods. There is one row for each access method supported
by the system.
Currently, only tables and indexes have access methods. The requirements for table
and index access methods are discussed in detail in Chapter 60 and
Chapter 61 respectively.
|Name of the access method|
|OID of a handler function that is responsible for supplying information about the access method|
Before PostgreSQL 9.6,
contained many additional columns representing properties of index access
methods. That data is now only directly visible at the C code level.
pg_index_column_has_property() and related
functions have been added to allow SQL queries to inspect index access
method properties; see Table 9.68.