Postgresql 中文操作指南
53.3. pg_am #
目录_pg_am_存储有关关系访问方法的信息。系统支持的每种访问方法都有一行。目前，只有表和索引具有访问方法。表和索引访问方法的要求分别在 Chapter 63和 Chapter 64中详细讨论。
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.
Table 53.3. pg_am Columns
Table 53.3. pg_am Columns
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. |
Note
在 PostgreSQL 9.6 之前，_pg_am_包含许多附加列，这些列表示索引访问方法的属性。现在，该数据只在 C 代码级别直接可见。但是，已添加了_pg_index_column_has_property()_和相关函数，以允许 SQL 查询检查索引访问方法属性；请参阅 Table 9.72。
Before 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 9.72.