PostgreSQL函数如果条件，然后运行查询，否则停止

Question

我需要以下Postgres功能的帮助

我有下表的列：

array, array_length

我最初有几个数组，然后运行查询（实际上是3个查询的集合），该查询选择数组，将其追加，然后将追加的数组插入表中。

我需要循环此插入查询，直到数组之一（ select max(array_length) from table ）达到预定义的大小，例如长度50。

我基本上需要写类似

begin 
for (select max(array_length) from table)<50
loop 
(drop table if exists super_item_temp;
ALTER TABLE super_item
    RENAME TO super_item_temp;

create table super_item as 
select distinct * from super_item_temp;

insert into super_item 
select ...calculations... from super_item)
end

但是我找不到正确的语法来写这个

我在http://www.postgresql.org/docs/8.4/static/plpgsql-control-structures.html上查看了该手册，但找不到任何有用的信息。

任何指向我正确方向的提示或链接将不胜感激！ 谢谢。

编辑：我试过

创建或替换功能function_name（）返回int4作为'DECLARE r RECORD;

开始时（从super_item中选择max（array_length）max）

loop
drop table if exists super_item_temp;
    ALTER TABLE super_item
        RENAME TO super_item_temp;

    create table super_item as 
    select distinct * from super_item_temp;


    insert into super_item 
    select old_array, 
    array_sort_unique( array_agg(added_item) || a.old_array) as new_array, 
    array_length(array_sort_unique( array_agg(added_item) || a.old_array),1)

    from (
            select 
    a.new_array as old_array,

    case when string_to_array(b.item2::text, ",")::int[] <@ a.new_array and string_to_array(b.item1::text, ",")::int[] <@ a.new_array then null
     when string_to_array(b.item2::text, ",")::int[] <@ a.new_array then b.item1 else b.item2 end  as added_item

    from

    super_item a 
    left join pairs b 

    on  string_to_array(b.item1::text, ",")::int[] <@ a.new_array or  string_to_array(b.item2::text, ",")::int[] <@ a.new_array /**any item from pair is in array**/
    where 1=1

    group by a.new_array, 2

    having sum(b.count)>10
    and sum(b.offset)<=0 
    and 
    case 
    when string_to_array(b.item2::text, ",")::int[] <@ a.new_array and string_to_array(b.item1::text, ",")::int[] <@ a.new_array then null
    when string_to_array(b.item2::text, ",")::int[] <@ a.new_array then b.item1 else b.item2 end is not null
    /**new item is not null**/
    order by 2 desc
    )a
    group by 1;
END LOOP;

返回1; 结束; '语言plpgsql;

SELECT function_name（）作为输出；

现在，我收到一个函数参数错误“未知列”，该参数应为带引号的分隔符。

错误：列„，“列第18行：在string_to_array（b.item1 :: text，“，”）:: int [] <@ a.new_ar ...

Answer 1

尝试一下，在我的PC上它可以正常编译（但是我不知道它是否按预期工作）。

CREATE OR REPLACE FUNCTION append_super_item ()
RETURNS integer AS $length$
declare
    length integer;
BEGIN
  WHILE (select max(array_length) from super_item)<50
    LOOP
       drop table if exists super_item_temp;
       ALTER TABLE super_item
            RENAME TO super_item_temp;
       Create table super_item as 
         select distinct * from super_item_temp;
       insert into super_item 
    select old_array, 
    array_sort_unique( array_agg(added_item) || a.old_array) as new_array, 
    array_length(array_sort_unique( array_agg(added_item) || a.old_array),1)

    from (
            select 
    a.new_array as old_array,

    case when string_to_array(b.item2::text, ",")::int[] <@ a.new_array and string_to_array(b.item1::text, ",")::int[] <@ a.new_array then null
     when string_to_array(b.item2::text, ",")::int[] <@ a.new_array then b.item1 else b.item2 end  as added_item

    from

    super_item a 
    left join pairs b 

    on  string_to_array(b.item1::text, ",")::int[] <@ a.new_array or  string_to_array(b.item2::text, ",")::int[] <@ a.new_array /**any item from pair is in array**/
    where 1=1

    group by a.new_array, 2

    having sum(b.count)>10
    and sum(b.offset)<=0 
    and 
    case 
    when string_to_array(b.item2::text, ",")::int[] <@ a.new_array and string_to_array(b.item1::text, ",")::int[] <@ a.new_array then null
    when string_to_array(b.item2::text, ",")::int[] <@ a.new_array then b.item1 else b.item2 end is not null
    /**new item is not null**/
    order by 2 desc
    )a
    group by 1;
    end loop;
end $length$ LANGUAGE plpgsql;