Greenplum 常用数据字典

一、数据库集群信息

1、gp_segment_configration

2、pg_filespace_entry

这两个表是在pg_global表空间下面的，是全局表。

用来查看集群segment信息，比如segment个数。

二、常用数据字典表

1、pg_class 

保存了所有表、视图、序列、索引元数据信息，每个DDL/DML操作都必须跟这个表发生关系。

2、pg_attribute

 

记录字段的内容

3、gp_distribution_policy

记录表的分布键

4、pg_statistic 和 pg_stats

数据库中表的统计信息保存在pg_statistic中

pg_stats可以方便帮我们查看pg_statistic的内容

5、pg_partition

记录分区表的信息

6、pg_partition_rule

分区表的分区规则

7、pg_partitions

三、字典表的应用

1、查看表的信息

1）从catalog中查询

 

2）从information_schema查询

select   *  from information_schema.tables where table_name ='';

1、获取字段信息

1）从catalog中查询

SELECT a.attname,pg_catalog.format_type(a.atttypid,( pg_catalog.pg_attribute a, a.atttypmod) AS data_type
FROM pg_catalog.pg_attribute a,
 (SELECT c. oid 
 FROM pg_catalog.pg_class c 
 LEFT JOIN pg_catalog.pg_namespace n 
 ON n.oid = c.relnamespace 
 WHERE c.relname = 'pg_class' 
 AND n.nspname = 'pg_catalog' 
 ) b  
WHERE a.attrelid = b.oid 
AND a.attnum > 0 
AND NOT a.attisdropped ORDER BY a.attnum; 

使用regclass就会简化很多：
SELECT a.attname,pg_catalog.format_type(a.atttypid, a.atttypmod) AS data_type
FROM pg_catalog.pg_attribute a
WHERE a.attrelid ='pg_catalog.pg_class'::regclass
AND a.attnum > 0
AND NOT a.attisdropped ORDER BY a.attnum;

2）从information_schema查询

select * from information_schema.columns where table_name = '';

2、获取表的分布键

select a.attrnums[i.i],b.attname,a.localoid::regclass

from gp_distribution_policy a,

(select generate_series(1,10))i (i),

  pg_attribute b

where a.attrnums[i.i) is not null

and a.localoid=b.attrelid

and a.attrnums[i.i]=b.attnum

and a.localoid='public.cxfa2 *::regclass order by i.i;

3、获取一个视图定义

testDB=# create table cxfa( a int) distributed by (a);
CREATE TABLE
testDB=# create view v_cxfa as select * from cxfa;
CREATE VIEW
testDB=# select pg_get_viewdef('v_cxfa', true);
SELECT cxfa.a FROM cxfa;
(1 row)

4、查询备注信息

 1）获取表的备注

select COALESCE(description, * *) as comment from pg_description where objoid=‘cxfa*::regclass and objsubid=0;

2）获取字段的备注

 select  b.attname as columnname, COALESCE(a.description,'') as comment 

from      pg_catalog.pg_description a,pg_catalog.pg_attribute b

where  objoid='cxfa'::regclass

and a.objoid=b.attrelid

and a.objsubid=b.attnum;

5、获取数据据库建表语句

1）调用plpythonu

CREATE PROCEDURAL LANGUAGE plpythonu;

2）创建存储过程

create or replace function get_table_structure(tablename text)    # 表名格式为 tableschema.table_name
    returns text
as $$
    try:
        table_name = tablename.lower().split('.')[1]

        talbe_schema=tablename.lower().split('.')[0]

    except (IndexError):

        return 'Please in put "tableschema.table_name"'

    get_table_oid="select oid,reloptions,relkind from pg_class where oid='%s'::regclass"%(tablename)

    try:

        rv_oid=plpy.execute(get_table_oid,5)      #plpy.execute(query [, max-rows])

        if not rv_oid:

            return 'Did not find any relation named"'+tablename +'".'

    except (Error):

        return 'Did not find any relation named"'+tablename +'".'