GreenPlum-查看表占用磁盘大小

背景

最近使用GreenPlum时，因为大量实验，遗留了很多或临时或正式的表，存储捉襟见肘。准备清理表时，第一件事就是查看表占用磁盘大小，从网上找了一些方法，比较靠谱的是这两篇

https://www.cnblogs.com/gobird/archive/2012/04/11/2442846.html

https://my.oschina.net/u/347414/blog/544187

使用

查询库占用磁盘大小

select pg_size_pretty(pg_database_size( 'MyDatabase' ));

查询表占用磁盘大小

普通表

select pg_size_pretty(pg_relation_size('relation_name')) ;

分区表

使用上面的语句去查分区表，会得到0bytes，就使用上文中创建的函数

-- Function: calc_partition_table(character varying, character varying)
 
-- DROP FUNCTION calc_partition_table(character varying, character varying);
 
CREATE OR REPLACE FUNCTION calc_partition_table(v_schemaname character varying, v_tablename character varying)
  RETURNS bigint AS
$BODY$
DECLARE
    v_calc BIGINT := 0;
    v_total BIGINT := 0;
    v_tbname VARCHAR(200);
    cur_tbname cursor for select schemaname||'.'||partitiontablename as tb from pg_partitions
   where schemaname=v_schemaname and tablename=v_tablename;
BEGIN
    OPEN cur_tbname;
    loop
        FETCH cur_tbname into v_tbname;
        if not found THEN
            exit;
        end if;
        EXECUTE 'select pg_relation_size('''||v_tbname||''')' into v_calc;
        v_total:=v_total+v_calc;        
    end loop;
    CLOSE cur_tbname;
    RETURN v_total;
end;
$BODY$
  LANGUAGE plpgsql VOLATILE;
ALTER FUNCTION calc_partition_table(character varying, character varying) OWNER TO gpadmin;

其中 gpadmin是你的username

然后使用select查询，如

select calc_partition_table ('public', 'test_partition_table')

PostgreSQL 提供了多个系统管理函数来查看表，索引，表空间及数据库的大小