雖然真的很雞肋,並且效能不雜滴,但聊勝於無吧.

drop function if exists exe_dynamic_sql(bigint);
drop function if exists exe_dynamic_count(bigint);
--返回記錄集
create or replace function exe_dynamic_sql(ival bigint)
    returns table(objectid bigint,name varchar(128))
as $$
	declare
	begin
		return query execute 'select objectid,name from dictionarys where parentid=$1 order by parentid,sort'
 
 using $1; 
	end;
$$ language plpgsql;

--賦值給變數
create or replace function exe_dynamic_count(ival bigint)
    returns bigint
as $$
	declare
		v_count bigint;
	begin
		execute 'select count(*) from dictionarys where parentid=$1' using $1 into v_count;
		return v_count;
	end;
$$ language plpgsql;
--測試
 

select * from exe_dynamic_sql(26);
select exe_dynamic_count(26);

要點:

• returns table(objectid bigint,name varchar(128)),定義返回的欄位和型別
• using $1執行時使用過程引數;

準備一個語句用於執行,這個就比較重要了,查詢引數繫結,開發利器

有朋友抱怨同一sql時快時慢,這是因為值在表中的佔比不同,佔比小的值就可以使用索引,值佔比超過5%裡sql就很慢了.此時就可以用下面的sql調式sql,可以根據不同的值來觀察執行計劃.

--getDictionarys僅在當前會話下有效
 

prepare getDictionarys (bigint) as
    select objectid,name from dictionarys where parentid=$1 order by parentid,sort;

explain (analyze,verbose,costs,buffers,timing)
execute getDictionarys(24);

explain (analyze,verbose,costs,buffers,timing)
execute getDictionarys(25);

explain (analyze,verbose,costs,buffers,timing)
execute getDictionarys(26);

--釋放指定的預備語句
deallocate getDictionarys;
--釋放所有預備語句
deallocate all;