The catalog 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 63 and Chapter 64 respectively.
pg_am
ColumnsBefore PostgreSQL 9.6, pg_am
contained many additional columns representing properties of index access methods. That data is now only directly visible at the C code level. However, pg_index_column_has_property()
and related functions have been added to allow SQL queries to inspect index access method properties; see Table 9.71.
Column Type
Description
oid
oid
Row identifier
amname
name
Name of the access method
amhandler
regproc
(references pg_proc
.oid
)
OID of a handler function that is responsible for supplying information about the access method
amtype
char
t
= table (including materialized views), i
= index.