从PostgreSQL数据库中检索注释

我正在Postgres数据库上运行一个项目,需要检索数据库中列的注释,以用作表格标题等.我已经看到有几个内置函数(pg_description和col_description),但我无法找到如何使用它们的例子,并且使用它们已经证明是徒劳的.

所以我想知道是否有人能够做到这一点,如果是这样,怎么样？

SELECT c.table_schema,c.table_name,c.column_name,pgd.description
FROM pg_catalog.pg_statio_all_tables as st
  inner join pg_catalog.pg_description pgd on (pgd.objoid=st.relid)
  inner join information_schema.columns c on (pgd.objsubid=c.ordinal_position
    and  c.table_schema=st.schemaname and c.table_name=st.relname);

这一切都是由oid工作的,

mat=> SELECT c.oid FROM pg_catalog.pg_class c WHERE c.relname = 'customers';
  oid  
-------
 23208
(1 row)

现在,我有那张桌子的oid,所以我可以问:

mat=> select pg_catalog.obj_description(23208);
  obj_description  
-------------------
 Customers
(1 row)

然后,我可以要求第四栏的描述:

mat=> select pg_catalog.col_description(23208,4);
             col_description             
-----------------------------------------
 Customer codes, CHS, FACTPOST, POWER...
(1 row)

如果您想知道在psql执行时运行了哪些查询,\dt+或者\d+ customers只是运行它-E.

注意模式,这段代码考虑它们:

SELECT
    cols.column_name,
    (
        SELECT
            pg_catalog.col_description(c.oid, cols.ordinal_position::int)
        FROM
            pg_catalog.pg_class c
        WHERE
            c.oid = (SELECT ('"' || cols.table_name || '"')::regclass::oid)
            AND c.relname = cols.table_name
    ) AS column_comment
FROM
    information_schema.columns cols
WHERE
    cols.table_catalog    = 'your_database'
    AND cols.table_name   = 'your_table'
    AND cols.table_schema = 'your_schema';

参考文献:

Postgresql文档表和列描述表和列的注释

在Postgres 9.1中确定表的OID？