数据仓库服务 GAUSSDB(DWS)-快速定位查询存储倾斜的表:场景一:磁盘满后快速定位存储倾斜的表

时间:2024-09-14 17:38:48

场景一:磁盘满后快速定位存储倾斜的表

首先,通过pg_stat_get_last_data_changed_time(oid)函数查询出近期发生过数据变更的表,介于表的最后修改时间只在进行IUD操作的CN记录,要查询库内1天(间隔可在函数中调整)内被修改的所有表,可以使用如下封装函数:

CREATE OR REPLACE FUNCTION get_last_changed_table(OUT schemaname text, OUT relname text)
RETURNS setof record
AS $$
DECLARE
row_data record;
row_name record;
query_str text;
query_str_nodes text;
BEGIN
query_str_nodes := 'SELECT node_name FROM pgxc_node where node_type = ''C''';
FOR row_name IN EXECUTE(query_str_nodes) LOOP
query_str := 'EXECUTE DIRECT ON (' || row_name.node_name || ') ''SELECT b.nspname,a.relname FROM pg_class a INNER JOIN pg_namespace b on a.relnamespace = b.oid where pg_stat_get_last_data_changed_time(a.oid) BETWEEN current_timestamp - 1 AND current_timestamp;''';
FOR row_data IN EXECUTE(query_str) LOOP
schemaname = row_data.nspname;
relname = row_data.relname;
return next;
END LOOP;
END LOOP;
return;
END; $$
LANGUAGE plpgsql;

然后,通过table_distribution(schemaname text, tablename text)查询出表在各个DN占用的存储空间。

1
SELECT table_distribution(schemaname,relname) FROM get_last_changed_table();
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