PostgreSQL强大的多层表继承--及其在海量数据分类按月分区存储中的应用(三)
RE' THEN
RETURN NULL;
END IF;
--Generate Table Name
str_sub_sample_time = date_part('year',NEW.sample_time)::varchar || '_' ||
CASE WHEN date_part('month',NEW.sample_time) <10 THEN '0' ELSE '' END
||date_part('month',NEW.sample_time)::varchar;
str_sub_tablename = 'machine2_' || str_sub_sample_time;
--Check if table not created
select * from pg_tables where schemaname = 'public' and tablename=str_sub_
tablename
tablename
into str_sql_cmd;
IF NOT FOUND THEN
--Create table Cmd
str_sql_cmd = '
CREATE TABLE '||str_sub_tablename||'
(
CONSTRAINT pk_'|| str_sub_tablename||' PRIMARY KEY (id ),
CONSTRAINT chk_'|| str_sub_tablename||'
CHECK(date_part(''year''::text, sample_time) = '||
date_part('year',NEW.sample_time)::varchar||
'::double precision AND
date_part(''month''::text, sample_time) = '||
date_part('month',NEW.sample_time)::varchar||'
)
)
INHERITS (base_table_machine2)
WITH ( OIDS=FALSE );
ALTER TABLE '||str_sub_tablename||' OWNER TO postgres;
CREATE INDEX idx_'|| str_sub_tablename||'_sample_time
ON '|| str_sub_tablename||'
USING btree (sample_time );
';
EXECUTE str_sql_cmd;
END IF;
--insert Data
str_sql_cmd = 'INSERT INTO '||str_sub_tablename||'
( id,dvalue,sample_time,machine_code,manu_id,manu_value) VALUES (
nextval(''serial_id_seq''),$1,$2,$3,$4,$5);
';
EXECUTE str_sql_cmd USING
NEW.dvalue,
NEW.sample_time,
NEW.machine_code,
NEW.manu_id,
NEW.manu_value;
--return null because main table does not really contain data
return NULL;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION on_insert_base_table_machine2()
OWNER TO postgres;
最后，为各个爸爸表设置触发器
[sql]
-
CREATE TRIGGER triggle_on_insert_machine1
-
BEFORE INSERT
-
ON base_table_machine1
-
FOR EACH ROW
-
EXECUTE PROCEDURE on_insert_base_table_machine1();
[sql]
-
CREATE TRIGGER triggle_machine2
-
BEFORE INSERT
-
ON base_table_machine2
-
FOR EACH ROW
-
EXECUTE PROCEDURE on_insert_base_table_machine2();
到此为止，我们可以分别向各个爸爸表（按类型分区表）插入数据，而后通过爷爷表（总表）
检索基本信息，通过爸爸表检索详细信息。对总表的操作会遍历反馈到所有子表，试图利用子表的
索引进行查询。由于按月存储，插入工作只限于本月，所以检索历史数据效率很高。
检索基本信息，通过爸爸表检索详细信息。对总表的操作会遍历反馈到所有子表，试图利用子表的
索引进行查询。由于按月存储，插入工作只限于本月，所以检索历史数据效率很高。