49.3. pg_am

The catalog pg_am stores information about relation access methods. There is one row for each access method supported by the system. Currently, only indexes have access methods. The requirements for index access methods are discussed in detail in Chapter 56.

Table 49.3. pg_am Columns

NameTypeReferencesDescription
oidoid Row identifier (hidden attribute; must be explicitly selected)
amnamename Name of the access method
amhandlerregprocpg_proc.oid OID of a handler function that is responsible for supplying information about the access method
amtypechar  Currently always i to indicate an index access method; other values may be allowed in future

Note

Before Postgres Pro 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 9.62.