greenplum分区表查看所占空间大小

在使用greenplum数据库的时候,有的时候想要查看表所占用空间的大小,会使用如下二个函数pg_relation_size和pg_size_pretty. 

前者用来查看数据大小,后者是human readable的调整.方法如下:

select pg_size_pretty(pg_relation_size('relation_name')) ;

select pg_size_pretty(pg_relation_size(oid)) ;

但是,对于分区表而言,这个方法就没有用了,会发现使用后表的大小为0bytes.原因在于:GP的分区表的主表只是一个表定义,其实际数据内容存储在继承父表的分区子表里面了.上网查了一下,没发现有相应的函数,干脆写了个函数来实现.

-- 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;